The spin directions of the Parity violated spin-splitting states in non-centrosymmetric compounds

The spin-directions and orientations are calculated for the Fermi surfaces of non- centrosymmetric compounds. Even in non-centrosymmetric compounds, each electron state is doubly degenerate by time reversal symmetry, but has the opposite spin-direction in the state with opposite sign of k-vector as its Kramers pair. For the states with high symmetry k- vector, the spin direction is determined by the symmetry, but not the orientation of the vector. Generally, to know the direction and the orientation of the spin, band structure calculations should be performed. The results are not as expected from so-called Rashba type spin-structure for the tetragonal CePt₃Si. In TaSi₂, the origin of anomalous magnetic breakdown effect might be related to its spin structure.