In some more complicated materials, we can have both a Hall conductivity and a longitudinal, usually isotropic, conductivity. Calculate the resistivity matrix \(R_{i j}\). Consider a transformation that acts by exchanging the values of the electric field components \(E_{i}\) and those of the current densities \(j_{i}\), and write it as a transformation on the complex value \(\sigma \equiv \sigma_{x y}+i \sigma_{x x}\).