Anomalous transport properties of dilute uranium alloys R1-xUxRu2Si2 (R = Th, Y; x≤0.07)

We investigate contribution of a single U ion to the electrical resistivity (Ap) in the dilute U alloys R1 - xUxRu2Si2 (R = Th,Y) for x less than or equal to 0.07. Contrary to the conventional Kondo behavior, in both systems hp exhibits an unusual decrease with reducing temperature below a characteristic temperature (T*) of similar to 10 K (R = Th) and 40 K (Y). At higher temperatures, Delta rho is almost independent of T with the amplitude (Delta rho(RT)) of similar to 59 (95) mu Omega cm/U for R = Th (Y). The dependence Delta rho similar to ln T below T* and the relationship Delta rho(T --> 0) similar to 1/2 Delta rho(RT) are found similarly between these two dilutions irrespective of T* and Delta rho(RT), suggesting that these are universal features in the dilute limit of URu2Si2. The ln T decrease in Ap is approximately proportional to the increase in the magnetic susceptibility, which provides a remarkable distinction between the present systems and known reverse-Kondo alloys. (C) 1999 Elsevier Science B.V. All rights reserved.