A rigorous spectral solution for three-dimensional (3D) electromagnetic sca
ttering by the edge of an anisotropic impedance half-plane with a perfect e
lectric conducting (PEC) face is presented. The surface impedance tensor of
the loaded face is characterised by: (i) principal anisotropy axes arbitra
rily oriented with respect to the diffracting edge; (ii) a vanishing surfac
e impedance along a principal anisotropy axis and an arbitrary impedance in
the orthogonal direction.