Fermion electric dipole moment operator ($\bar{\psi }{\sigma }^{\mu \nu }{\gamma }^5\psi F_{\mu \nu }$)

The fermion electric dipole moment operator couples a fermion pseudotensor bilinear to the electromagnetic field tensor. Its nonrelativistic interaction is proportional to $\mathbf{S}\cdot \mathbf{E}$, so it is odd under parity and time reversal and signals CP violation.