RESISTIVITY AND MAGNETORESISTANCE OF (U1-XMX)BE13 (M = LA,TH,Y,SC,HF)

Electrical resistivity and longitudinal magnetoresistance of (U(1-x)M(x))Be13, with M = La, Th, Y, Sc, and Hf, were investigated in the temperature range 0.4-300 K and fields to 14 T. Alloying-caused changes of the resistivity can be correlated with variations of U-Be separation, or localization or delocalization of U 5f states. The large, negative magnetoresistance of UBe13 is severely depressed when only a minor, approximately 5%, amount of impurities are introduced for U. The changes of magnetoresistance, for x less-than-or-equal-to 0.05, cannot be related to either lattice-pressure effects or the electronic configuration of M. It is suggested that the large, negative magnetoresistance, similarly to the enhanced specific heat, results from intersite 5f correlations existing in UBe13 at low temperatures.