Resistivity and Magnetoresistance of La-doped CeOs₄Sb₁₂and PrOs₄Sb₁₂

Abstract

The resistivity and magnetoresistance of La-doped CeOs4Sb12 and PrOs4Sb12 were investigated at temperatures down to 20 mK and in magnetic fields up to 18 T. The resistivity of Ce0.98La0.02Os4Sb12, in fields smaller than 4 T, has a Kondo-hole impurity temperature variation, i.e., ρ = ρ0 + AT 2 , with a negative and strongly field-dependent A. However, the positive magnetoresistance suggests that this anomalous behavior is due to Kondo-hole bands. The magnetoresistance of La-doped PrOs4Sb12 confirms the singlet CEF ground state of Pr. Furthermore, its field variation and near isotropy argue against lowest-level crossing along any crystallographic direction. Instead, the results suggest avoided level crossing for all directions of the magnetic field. The possible origin of a dome-like shape in the magnetoresistance of the pure Pr compound is discussed.