LOW-TEMPERATURE MAGNETIC-PROPERTIES OF UAL2 - THE KONDO EFFECT

We have measured the specific heat in the temperature range between 1.5 and 50 K on UAl2, classified as a paramagnetic 5f heavy fermion compound. A pronounced Schottky-like peak is observed at about 40 K with the peak height of 6 J/K mol in the electronic specific heat. Moreover, T3 ln T temperature dependence in the specific heat is strongly suppressed below about 9 K in the case of U(Al1-ySiy)2 (0<yless-than-or-equal-to0.10), whereas no apparent change is observed for (U1-xPrx)Al2 (0<xless-than-or-equal-to0.15). The electronic specific heat coefficient, gamma, is considerably enhanced with increasing Pr concentration. The gamma-value and the inverse of the absolute value of the paramagnetic Curie temperature both for (U1-xPrx)Al2 and U(Al1-ySiy)2 are varied with the lattice parameter. These behaviors are understood within the framework of the Kondo effect.