Electrical resistivity and thermoelectric power study of the heavy-fermioncompounds (CexLa1-x)(7)Ni-3

Ac magnetic susceptibility, electrical resistivity and thermoelectric power have been measured for (CexLa1-x)(7)Ni-3 (0 less than or equal tox less th an or equal to1). The Neel temperature is 1.8 K for x=1, decreases with dec reasing x and disappears around x = 0.43. At high temperatures above 60 K t he magnetic resistivity p(m) shows - In T dependence and the values of slop es are constant with x down to 0.2. The magnetic resistivity p(m) at 1.5 K is decomposed into a Nordheim contribution term and a term of the incoheren t Kondo effect influenced by magnetic interaction. The unitarity limit valu e is 388 mu Omega cm/Ce. The thermoelectric power S(T) has a large negative peak at 5 K for x = 1. For small substitutions of La for Ce (x = 0.9), the negative peak vanishes and a positive peak dire to the Kondo contribution appears near 6 K. The magnitude of the positive peak increases with decreas ing x down to 0.7 and decreases down to 0.1. The S(T) curve for x = 0.1 is remarkably different, with a phonon-drag around 30 K for La7Ni3 (x = 0). A broad minimum exists around 40 K for all concentrations except for x = 0. T his is probably due to crystal field excitations. The results in the presen t study are discussed in terms of a competition between the magnetic intera ction and the Kondo interaction. (C) 2001 Elsevier Science B.V. All rights reserved.