The spin-orbit interaction was taken into account in a fully non-collinear approach. These simulations were performed for the atomic coordinates of the conventional cell provided by Materials Project (mpID 1223443) that we converted to a primitive unit cell using AFLOW/ACONVASP. We subsequently relaxed the atomic coordinates until all forces were less than 5 meV/Å. We used a 12 × 12 × 12 Γ-centered k-point grid for the Brillouin zone integration when computing the PBE electronic structure, a Gamma centered 4 × 4 × 4 grid for the HSE06 data, and a Gamma centered 16 × 16 × 16 grid for optical spectra.