Temperature dependence of the electrical resistivity and thermopower of U2Ni2In and Nd2Ni2Sn

Accurate measurements of the electrical resistivity (p,dp/dT) and of the thermoelectric power (S,dS/dT) were performed in the ternary compounds U2Ni2In and Nd2Ni2Sn from 4 K to 250 K, and the results are compared with those previously obtained in U2Ni2Sn. The pair U2Ni2In/U2Ni2Sn enables us to study the influence of the p-electron character (and other band effects related to the elements In/Sn) on the transport properties, whereas the pair Nd2Ni2Sn/U2Ni2Sn provides direct information on the role played by the 4f/5f electrons. All these compounds order initially in the antiferromagnetic state, exhibiting a characteristic minimum 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 transitions below T-N, Of first-order character and likely associated with order-order magnetic transitions. The anomalous behavior of p(T) in the paramagnetic phase of the Nd2Ni2Sn compound can be satisfactorily described in terms of crystal field effects associated with the 4f-electron levels. (C) 1996 American Institute of Physics.