Time-Reversal Degeneracies in the Band Structure of a Ferromagnetic Metal

Symmetry of a single domain of a ferromagnetic metal should be described by the appropriate magnetic (Shubnikov) space group M. Previous workers have used only the unitary subgroup of M. It is shown here that the inclusion of the antiunitary elements of M may lead to some degeneracies, beyond those noted previously, in the electronic band structure for a hexagonal close-packed metal, but not for a cubic metal.