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A metallic room-temperature d-wave altermagnet

Abstract

Altermagnetism is a recently discovered unconventional magnetic phase that is characterized by time-reversal symmetry breaking and spin-split band structures in materials with zero net magnetization. Recently, spin-polarized band structures and a vanishing net magnetization were observed in semiconductors MnTe and MnTe2, confirming this unconventional magnetic order. Metallic altermagnets offer advantages for exploring physical phenomena related to low-energy quasiparticle excitations and for applications in spintronics because the finite electrical conductivity of metals allows direct manipulation of the spin current through the electric field. We demonstrate that KV2Se2O is a metallic room-temperature altermagnet with d-wave spin-momentum locking. Our experiments probe the magnetic and electronic structures of this compound and reveal a highly anisotropic spin-polarized Fermi surface and the emergence of a spin-density-wave order in the altermagnetic phase. These characteristics suggest that KV2Se2O could be a helpful platform for high-performance spintronic devices and for studying many-body effects coupled with unconventional magnetism.

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Fig. 1: Magnetic structure characterization.
Fig. 2: Electronic structure of the altermagnetic configuration.
Fig. 3: SARPES data.
Fig. 4: Electronic structure in the SDW phase.

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Data availability

All the data are available from the corresponding authors upon reasonable request. Source data are provided with this paper.

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Acknowledgements

We thank J. Liu, W. Yu, R. Zhou and C. Fang for fruitful discussions. We thank L. Deng and S. Qiao for assistance with the SARPES experiments at the Shanghai Institute of Microsystem and Information Technology. This work was supported by the Ministry of Science and Technology of China (Grant Nos. 2022YFA1403800, 2023YFA1406100, 2022YFA1403903, 2022YFA1602800, 2021YFA1401903, 2022YFA1403400, 2021YFA1400401 and 2022YFA1403100), the National Natural Science Foundation of China (Grant Nos. U22A6005, 11925408, 11921004, 12134018, 12188101, 12204222, 12204297, 12274440 and 12374143), the Chinese Academy of Sciences (Grant No. XDB33000000), the K. C. Wong Education Foundation (Grant No. GJTD-2020-01), the Zhejiang Provincial Natural Science Foundation of China (Grant No. LD24F040001) and the Synergetic Extreme Condition User Facility. We acknowledge the beam time at the GPPD granted by the China Spallation Neutron Source, at the BL09U and BL03U beamlines at the Shanghai Synchrotron Radiation Facility and at the Shanghai Institute of Microsystem and Information Technology. H.W. acknowledges support from the New Cornerstone Science Foundation through the Xplorer Prize. Y.H. acknowledges support from the Shanghai Municipal Science and Technology Major Project and the Shanghai Committee of Science and Technology (Grant No. 23JC1403300).

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Contributions

T.Q., H.W. and H.L. supervised the project. B.J., M.H., H.L. and T.Q. performed the ARPES and SARPES experiments with assistance from G.Q., Y.H. and W.L. J.B., W.Z. and G.C. synthesized the single crystals. Z.S., H.P. and H.W. performed the density functional theory calculations. C.M., Z.L. and J.L. performed the NMR experiments. L.H. and S.L. performed the neutron diffraction experiments. X.Z. and Y.P. performed the X-ray diffraction experiments. Z.W. and Y.S. performed the scanning tunnelling microscopy experiments. B.J., M.H., H.L. and T.Q. analysed the experimental data. B.J., M.H., Z.S., H.L. and T.Q. plotted the figures. T.Q. and H.L. wrote the manuscript with contributions from all authors.

Corresponding authors

Correspondence to Zheng Li, Genfu Chen, Hang Li, Hongming Weng or Tian Qian.

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Extended data

Extended Data Fig. 1 Single crystal X-ray and powder neutron diffraction data.

a, (K, L) map of reciprocal space at H = 1 measured at 80 K. The double peaks originate from the small non-monochromaticity of the Mo x-ray source, which consists of Kα1 (17.48 keV) and Kα2 (17.37 keV), and bremsstrahlung. The bright and sharp diffraction peaks indicate that the samples are of high quality with only one crystalline phase. b, Observed XRD intensities from 143 indexed Bragg peaks compared with the calculations based on the crystal structure with space group P4/mmm. c, Powder neutron diffraction spectrum at 300 K refined to the crystal structure with space group P4/mmm. The observed (Iobs) and calculated (Ical) patterns and the difference between them (Iobs - Ical) are plotted.

Source data

Extended Data Fig. 2 Calculated orbital- and spin-resolved band structures along high-symmetry lines.

Red and blue dots represent spin-up and spin-down bands. The size of the dots scales the projection of orbital components.

Source data

Extended Data Fig. 3 Electronic structure in the 3D BZ.

a, Calculated spin-resolved FSs at kz = π. Red and blue curves are spin-up and spin-down FSs. Black dashed lines indicate the BZ boundary. b, Calculated spin-resolved band structure along high-symmetry lines at kz = 0 (solid curve) and π (dashed curve). Red, blue, and green curves are spin-up, spin-down, and spin-degenerate bands. c, ARPES intensity plot at EF measured along Γ–X with varying photon energy, showing FSs in the ky = 0 plane. Vertical dashed lines and arrows indicate negligible kz dispersion of the FSs. d, Comparison of the ARPES data taken at 20 K with the calculated bands at kz = π. The spectra are a sum of the data collected under LH and LV polarizations (Extended Data Fig. 8) with = 67 eV. Dashed curves are shifted upward by 90 meV for better matching the experimental data.

Source data

Extended Data Fig. 4 Spin-resolved band structures at kz = 0 without (left) and with (right) SOC.

Opposite spin polarization components along the c axis are indicated by a red-blue color scale.

Source data

Extended Data Fig. 5 Calculated band structures along \(\bar{\Gamma }-\bar{{\rm{M}}}\) at kz = 0.4π (red line in a) without (b) and with (c) SOC.

The inset in c shows a zoom-in view of the bands within the black square.

Source data

Extended Data Fig. 6 Tight-binding calculations.

a, Tight-binding calculations of the bands derived from the V1 dxz (dashed curves) and V2 dyz orbitals (solid curves) in the nonmagnetic phase. b, Tight-binding calculations of the bands derived from the V dxz (dashed curves) and the V dyz orbitals (solid curves) in the magnetically ordered phase. Red and blue represent spin-up and spin-down polarizations. c, Schematic of the V dxz and V dyz orbitals, which form δ and π bonds, respectively, along the b axis.

Source data

Extended Data Fig. 7 Polarization-dependent ARPES data.

a-c, ARPES intensity plots along Γ−X, Y−M and Γ−M measured at 20 K with hv = 67 eV under LV polarization. d-f, Same as a-c but measured with LH polarization. Red, blue, and green dashed curves are spin-up, spin-down, and spin-degenerate bands at kz = 0.

Source data

Extended Data Fig. 8 Comparison of the ARPES data taken at 120 K with the calculated bands at kz = 0 (a) and π (b).

The ARPES spectra are a sum of the data collected under LH and LV polarizations with = 67 eV. Red, blue, and green dashed curves are spin-up, spin-down, and spin-degenerate bands.

Source data

Extended Data Fig. 9 Spin-resolved ARPES results of the topological surface state of Bi2Se3.

a, ARPES intensity plot showing band dispersions across \(\bar{\Gamma }\). b, Spin-resolved MDCs at an energy indicated by black dashed line in a. Red and blue curves are spin-up and spin-down signals. c, Momentum-dependent spin polarizations calculated by the asymmetry of the spin-up and spin-down signals in b. Red and blue filled areas highlight the spin-up and spin-down polarizations.

Source data

Extended Data Fig. 10 Gapless FS pocket at the Y point.

a, Symmetrized ARPES spectra along M–Y–M at 20 K. b, Symmetrized EDCs at 20 K at the kF points marked by dashed lines in a. c, Symmetrized EDCs at the kF point #3 in a at different temperatures.

Source data

Source data

Source Data Fig. 1

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Source Data Extended Data Fig. 1

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Compressed file containing processed experimental data for Extended Data Fig. 2.

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Compressed file containing processed experimental data for Extended Data Fig. 3.

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Compressed file containing processed experimental data for Extended Data Fig. 4.

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Compressed file containing processed experimental data for Extended Data Fig. 5.

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Compressed file containing processed experimental data for Extended Data Fig. 6.

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Compressed file containing processed experimental data for Extended Data Fig. 8.

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Compressed file containing processed experimental data for Extended Data Fig. 9.

Source Data Extended Data Fig. 10

Compressed file containing processed experimental data for Extended Data Fig. 10.

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Jiang, B., Hu, M., Bai, J. et al. A metallic room-temperature d-wave altermagnet. Nat. Phys. 21, 754–759 (2025). https://doi.org/10.1038/s41567-025-02822-y

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