IMPURITY EFFECTS ON THE LOW-TEMPERATURE PROPERTIES OF UAL2

We have measured the magnetization of pure UAl2 below 1 K down to 0.1 K and the effects of impurities on the susceptibilty and specific heat in the temperature range 2-370 K for the susceptibility and 1.5-20 K for the specific heat. The magnetization of UAl2 shows a slight upturn in the curvature below 1 K with respect to the applied magnetic field. This behavior is quite similar to that of CeRu2Si2 below the critical field of the metamagnetic-like jump. Silicon impurities suppress the enhancement of the electronic specific heat coefficient, in contrast with the case of praseodymium.