Exotic Kondo-hole band resistivity and magnetoresistance of Ce1-xLaxOs4Sb12 alloys

Electrical resistivity measurements of nonmagnetic single-crystalline Ce1-xLaxOs4Sb12 alloys, x=0.02 and 0.1, are reported for temperatures down to 20 mK and magnetic fields up to 18 T. At the lowest temperatures, the resistivity of Ce0.98La0.02Os4Sb12 has a Fermi-liquid-like temperature variation rho=rho(0)+AT(2) but with negative A in small fields. The resistivity has an unusually strong magnetic field dependence for a paramagnetic metal. The 20 mK resistivity increases by 75% between H=0 and 4 T and then decreases by 65% between 4 and 18 T. Similarly, the A coefficient increases with the field from -77 to 29 mu Omega cm K-2 between H=0 and 7 T and then decreases to 18 mu Omega cm K-2 for 18 T. This nontrivial temperature and field variation is attributed to the existence of a very narrow Kondo-hole band in the hybridization gap, which pins the Fermi energy. Due to disorder, the Kondo-hole band has localized states close to the band edges. The resistivity for x=0.1 has a qualitatively similar behavior to that of x=0.02 but with a larger Kondo-hole band.