A systematic ab initio study, using the local spin density approximation, of the electronic properties of Ga x P y M compounds, where M is a transition metal substituting Ga or P atoms in a GaP host semiconductor lattice is presented. This study is oriented towards the early identification of intermediate band materials of recent interest as new photovoltaic materials to exceed the efficiency of single gap and even tandems of two solar cells. M=Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn have been explored as transition metals and Sc, V, Cr, and Fe in Ga 32 P 31 M and Cr in Ga 31 P 32 M have exhibited the desired intermediate band.