Fig. 1: Crystal structure and electronic structure of SmAlSi.
a Crystal structure of SmAlSi where the blue triangles indicate the co-planar Al and Si atoms. b Bulk BZ (red) and the (001) surface projected BZ (orange). c and d Density functional theory (DFT) calculation of the bulk electronic band structure of SmAlSi without and with spin-orbit coupling (SOC), respectively. Kramers nodal lines along Γ − Z are highlighted in blue and the 4-fold degeneracies at Z are circled in red. The two pair of zoom-in boxes are to emphasize the effect of SOC splitting. The complete DFT plots can be found in Fig. S2. e Room temperature polarization-resolved optical second harmonic generation (SHG) measurements under 45 degree incidence on the (001) facet showing broken inversion symmetry. The parallel (red) and crossed (blue) curves are measured by keeping the incident and detecting polarizations parallel and perpendicular, respectively. f The magnetic susceptibility (filled blue symbols) measured at μ0H // c = 0.1 T (left axis). The inverse susceptibility (open blue symbols) is shown with a Curie-Weiss fit (red line) (right axis). g Electrical resistivity as a function of temperature at H = 0. The inset shows a zoom-in view of the two transitions. h d(MT)/dT (blue), dρ/dT (black), and specific heat Cp (red) showing two transitions at TN and T1.
