Ce3CuxPt3-xSb4: Modifying the properties of a Kondo insulator by substitutional doping

The temperature dependence of the magnetic susceptibility, thermopower, and electrical resistivity were explored for the solid solution Ce3CuxPt3-xSb4 . The magnetic susceptibility varies from Ce3+ Curie-Weiss behavior in Ce3C u3Sb4 to almost Ce4+ behavior (intermediate valence) in Ce3Pt3Sb4. All samp les had semiconducting resistivities with decreasing activation energies fo r higher copper concentrations. The large positive thermopower of Ce3Pt3Sb4 is greatly affected by small concentrations of copper. The peak of similar to 300 mu V/K at approximately 110 K for Ce3P3,Sb-4 changes to approximate ly -170 mu V/K for Ce3Cu0.5Pt2.5Sb4 at the same temperature. For all the co pper-doped samples, the thermopower changes from positive to negative value s on cooling. [S0163-1829(99)14831-8].