TEMPERATURE-DEPENDENCE OF THE ELECTRICAL-RESISTIVITY AND THERMOPOWER OF U2NI2IN AND ND2NI2SN

Accurate measurements of the electrical resistivity (p,dp/dT) and of t he thermoelectric power (S,dS/dT) were performed in the ternary compou nds U2Ni2In and Nd2Ni2Sn from 4 K to 250 K, and the results are compar ed with those previously obtained in U2Ni2Sn. The pair U2Ni2In/U2Ni2Sn enables us to study the influence of the p-electron character (and ot her band effects related to the elements In/Sn) on the transport prope rties, whereas the pair Nd2Ni2Sn/U2Ni2Sn provides direct information o n the role played by the 4f/5f electrons. All these compounds order in itially in the antiferromagnetic state, exhibiting a characteristic mi nimum in dp/dT at T-N. In the U2Ni2In compound a drastic reduction is observed in p(T) slightly below T-N, suggesting the coexistence of the antiferromagnetic state with a coherent Kondo effect when T less than or equal to 0.8 T-N. In Nd2Ni2Sn we observe distinct phase transition s below T-N, Of first-order character and likely associated with order -order magnetic transitions. The anomalous behavior of p(T) in the par amagnetic phase of the Nd2Ni2Sn compound can be satisfactorily describ ed in terms of crystal field effects associated with the 4f-electron l evels. (C) 1996 American Institute of Physics.