The diffraction problem involving an arbitrary-angled perfectly conducting wedge that is coated by a lossy metamaterial slab is solved in the case of plane waves at normal incidence. The solution works in the context of the uniform theory of diffraction and is obtained by means of an analytical procedure that is based on the use of electric and magnetic equivalent surface currents evaluated under the physical optics approximation. The expressions of the diffraction coefficients are manageable since they are in closed form and contain the geometrical optics response of the structure and the transition function of the uniform theory of diffraction. The corresponding diffracted field is able to compensate the geometrical optics discontinuities...