Spectroscopic evidence for spin splitting in a collinear antiferromagnet*

The Anomalous Hall effect (AHE) has been understood in close relation to nontrivial band topology. Recently, it has been proposed that AHE can arise in compensated collinear magnets with opposite-spin sublattices connected by rotational symmetry. This distinct magnetic phase, so-called 'altermagnetism', is characterized by time-reversal symmetry (TRS) broken electronic structure with non-relativistic spin-momentum locking. We performed angle-resolved photoemission spectroscopy (ARPES) on semiconducting MnTe, an altermagnetic candidate. Spin-split electronic structure with a large splitting of ~1 eV is clearly resolved. The compensated magnetic semiconductor with TRS-broken electonic structure provides a new platform for novel topological spintronics.