TRANSPORT-PROPERTIES OF CE2NI2SN AND CE2PD2.05SN0.95 KONDO-LATTICE SYSTEMS

We report experimental data on thermoelectric power S, electrical resi stivity rho, and the magnetoresistivity of the antiferromagnet Kondo s tannides Ce2Ni2Sn (T-N = 4.7 K) and Ce2Pd2.05Sn0.95 (T-N = 4.7 K). The essential features of the S(T) curves resemble those of heavy fermion systems such as CeCu2Si2: a broad and positive maximum at intermediat e temperatures, followed by a sharper negative minimum at lower temper atures. S values are is considerably smaller in Ce2Pd2.05Sn0.95 than i n Ce2Ni2Sn. The positive peak originates from the incoherent Kondo sca ttering by the excited crystal field levels of the Ce ion ground state . The negative peak might be related to the shape of the density of st ates associated with the Abrikosov-Suhl resonance. The change of sign in S(T) between its minimum and maximum at T can be assigned to the f act that the Fermi level sinks below the upper band at T > T. This be havior and the maximum observed in the rho(T) curve at this temperatur e can be discussed in terms of the electron polaron model, although on e must also take into account the crystal field effect. The role playe d by the crystal held effect, which is more important in Ce2Pd2.05Sn0. 95, is analyzed for this compound, providing the magnitude of the crys tal field splitting. Magnetoresistivity was also measured in both comp ounds. The results are consistent with the important role of the Kondo effect at low temperatures and suggest the splitting of the double de generate bands at T > T. (C) 1997 American Institute of Physics.