We report a study of the optical properties of a mixture of spherical inclusions within a host continuum. The structure of the designed SiC/AZO material is a binary composite of two different kinds of nano spheres, one made from a semiconductor material (SiC) and the other from a plasmonic material (AZO). Its electromagnetic response is studied using the extended Maxwell–Garnett effective medium theory and a rigorous method based on layer-multiple-scattering theory. A very nice agreement between both treatments is established, rendering the effective medium approximation a useful guide for the experimentalist in the field.