Observation of an Energy- and Temperature-Dependent Carrier Mass for Mixed-Valence Ce${\mathrm{Pd}}_3$

The far-infrared conductivity of Ce${\mathrm{Pd}}_3$ has been obtained from temperature-dependent reflectivity measurements between 0.4 and 400 meV. The low-temperature results are consistent with simple Fermi-liquid ideas, even though the conduction-carrier density is less than 0.3 electron per formula unit.