Synmmetry of electron states in antiferromagnetics

The symmetry of electron states in an antiferromagnetically ordered crystal is investigated using the elements of the two-value corepresentation method for magnetic groups in a form corresponding to microscopy-theory methods. Symmetry restrictions on the quasi-particle spectra, on their interaction with the magnetic field, and on the interband matrix elements are found. The results obtained are illustrated for a two-dimensional system corresponding to the CuO2 plane in weakly doped high-temperature superconductors.