Kramers degeneracy in a magnetic field and zeeman spin-orbit coupling in antiferromagnetic conductors

In this article, I study magnetic response of electron wavefunctions in a commensurate collinear Néel antiferromagnet. I show that, at a special set of momenta, hidden anti-unitary symmetry protects Kramers degeneracy of Bloch eigenstates against a magnetic field, pointing transversely to staggered magnetization. Hence a substantial momentum dependence of the transverse g-factor in the Zeeman coupling, turning the latter into a Zeeman spin-orbit interaction, that may be present in materials from chromium to borocarbides, cuprates, pnictides, as well as organic and heavy fermion conductors.