  According to the Onsager principle a matrix of kinetic coefficients is
symmetric in a system not violating time inversion symmetry. The antisymmetry
is possible in systems with broken time inversion symmetry f.i. in systems in
external magnetic field. An exception to this rule is presented here. It is
shown that in a tetragonal metals with point group $C_{4v}$ not violating time
inversion the conductivity tensor is antisymmetric. The corresponding optical
properties are considered.
