Resistivity and Magnetoresistance of La-doped CeOs4Sb12and PrOs4Sb12

Abstract

The resistivity and magnetoresistance of La-doped CeOs 4 Sb 12 and PrOs 4 Sb 12 were investigated at temperatures down to 20 mK and in magnetic fields up to 18 T. The resistivity of Ce 0.98 La 0.02 Os 4 Sb 12 , in fields smaller than 4 T, has a Kondo-hole impurity temperature variation, i.e., ρ=ρ 0 + A T 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 PrOs 4 Sb 12 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.