Electronic structure and transport properties of ternary skutterudite: CoX_3/2Y_3/2

Electronic properties of ternary skutterudites AX_3/2Y _3/2 (A=Co, X=Ge, Sn and Y=S, Te) are investigated using first principles calculations to clarify recent experimental results. Band derivatives are computed accurately within an approach based on Maximally Localized Wannier Functions (MLWF5). Band structures exhibit larger effective masses compared to parental binary CoSb₃. Our results also indicate a more parabolic dispersion near the top of the valence band and a multivalley character in both conduction and valence band. Despite the improved thermopower these skutterudites has relatively low power factor due to increased resistivity. The fundamental cause of such large resistivity seems to be associated with the ionicity of the bonding.