Anomalous Temperature Dependence of the Electrical Resistivity in R3co4ge13 (R = Y, Lu) Single Crystals

Abstract

The presence of strong disorder can significantly impact electrical conduction in metallic systems. Here, we investigate the temperature dependence of the electrical resistivity, ρ(T), in nonmagnetic single crystals of the Remeikaphase cage compounds R3Co4Ge13 (R = Y, Lu). Contrary to the density of states (DOS) calculations in the literature, the experimentally measured ρ(T) in both compounds exhibits semiconducting-like behavior, which we attribute to strong intrinsic disorder. A detailed analysis of the electrical resistivity data reveals that neither the Arrhenius thermal activation law nor variable-range hopping (VHR) models can adequately describe their temperature dependence over the broad temperature range of 2-350 K. However, a model incorporating parallel conduction through both semiconducting and metallic channels provides an adequate explanation. In addition to a dominant metallic conduction below ∼ 10 K, a negative temperature coefficient of the electrical resistivity (dρ/dT) is found in both samples. In the absence of magnetic impurities, the observed dρ/dT < 0 is interpreted in terms of the structural Kondo mechanism.

Keywords: Single crystal growth, x-ray diffraction, Electrical transport, Two-channel electrical conduction, structural Kondo Mechanism, Remeika phase