Negative-temperature coefficients of electrical resistivity in amorphous La-based alloys

A negative-temperature coefficient (=-1d dT) of electrical resistivity, (T), has been observed in many amorphous and disordered metallic conductors. The origin of this anomalous temperature dependence of resistivity is still unclear. To explain the negative- anomaly, there are two theoretical approaches (i.e., the Ziman-type theory and the structural Kondo model) currently discussed in the literature. In an attempt to distinguish between these two approaches the resistivity of several liquid-quenched amorphous La-based alloy systems containing Al, Au, Ga, or Ge, has been analyzed as a function of composition and temperature. It is concluded that the resistivity data are inconsistent with the Ziman-type theory and are in favor of the structural Kondo-type model. This conclusion is based on the fact that (1) resistivity varies as -lnT (T100 K) in alloys with negative, and (2) the occurrence of negative is independent of the valence of the La-based alloys. © 1980 The American Physical Society.