Nonrelativistic Spin Splitting at the Brillouin Zone Center in Compensated Magnets.

The nonrelativistic spin-splitting (NRSS) of electronic bands in "altermagnets" has sparked renewed interest in antiferromagnets (AFMs) that have no net magnetization. However, altermagnets with collinear and compensated magnetism are not the only type of NRSS AFMs. In this Letter, we identify the symmetry conditions and characteristic signatures of a distinct group of NRSS AFMs that go beyond the description of altermagnets. These compounds exhibit a broken spin degeneracy among the spin-polarized bands at the Γ point in the absence of spin-orbit coupling. We use density functional theory calculations to validate these models in ternary magnetic nitrides, specifically MnXN_{2} (X=Si, Ge, Sn), and their cation ordered variants. By removing the previous spin degenerate constraint at Γ, these compounds may facilitate the generation of spin currents without cancellation arising from the alternating spin polarizations. Our findings expand the scope of NRSS eligible materials.