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Whilst strong coupling between structure and magnetism is a signature of many of the Fe-based superconductors, no evidence for this has been reported in the normal state of FeSe. Here, the authors demonstrate strong coupling between nematicity and magnetism in FeSe under applied pressure.

The interplay between magnetic and superconducting phases is important to understand the physics of iron-based superconductivity. Here, the authors use thermodynamic measurements on Ba_1−xK_xFe₂As₂ single crystals to provide details of its phase diagram and the re-entrance of a C₂spin-density-wave phase.

Fe-based superconductors have attracted tremendous interest recently. New evidence on BaFe₂As₂ shows that chemical doping and pressure, both of which induce superconductivity, distort the lattice in similar ways. The result provides important information in the quest for an understanding of the mechanism behind superconductivity.

Charge–density–wave correlations, quantum oscillations and Fermi-liquid charge transport are at the centre of a heated debate in cuprate superconductivity. Using resonant X-ray scattering, Tabis et al. investigate the charge order and its link to the electronic transport properties in HgBa₂CuO_4+δ.

Functional magnetic materials with large anisotropy and coercivity, which are not based on scarce rare earth elements, are much sought after. Here, the authors show that the material Li₂(Li_1–xFe_x)N, which has similar properties as single-molecular magnets, shows those interesting properties.

Magnetic symmetry is a vital factor to determine exotic topological phases. Here, Riberolles et al. demonstrate a helical antiferromagnetic order in EuIn₂As₂ which makes it a magnetic topological-crystalline axion insulator.

The interplay between superconductivity and charge density wave (CDW) in 2H-NbSe₂ is still not fully understood. Here, Cho et al. use controlled disorder to probe the interplay between these two phases in 2H-NbSe₂ and find that superconductivity initially competes with CDW but eventually long-range CDW order assists superconductivity.

The ability to control the magnetic order in a material with an electric field will enable low-power non-volatile memories and new types of computer logic. Ryanet al. demonstrate that europium titanate under moderate strain exhibits strong magnetoelectric coupling that could be valuable to this endeavour.

In the cuprates, antiferromagnetic correlations might be the cause of the pseudogap phenomenon. Here the authors use neutron scattering on the tetragonal cuprate HgBa₂CuO_4+δrevealing commensurate antiferromagnetic excitations as a signature of the pseudogap state.

Nematic order in the iron-based superconductors breaks the symmetry between the x and y directions in the Fe plane. Beyond this, however, there is little consensus on how nematic order arises and whether it has an effect on superconductivity. This Review discusses the current theoretical and experimental state of the field.