Axial tensor is even under the inversion operation. This kind of tensor is suitable for circular photogalvanic effect (CPGE), Edelstein effect, magnetoelectric effect
There is only the even part () for grey MPGs (the second ones of each row, with ), and the odd and even parts () and ) have same symmetry in original MPGs (the first MPGs of each row, without ).
The subscript number of the tensor means the independent element number.
is zero for the original and grey groups not listed here because they have the inversion symmetry.