Conductivity and thermopower of heavy fermion systems with disorder

We investigate the influence of disorder (impurities) on the electronic (transport) properties of heavy fermion systems, which are described by the periodic Anderson model (PAM). In this paper we consider disorder within the conduction band. The PAM is mapped onto an effective single impurity Anderson model (SIAM) by dynamical mean-field theory (DMFT), and the modified perturbation theory (MPT)-an approximation that is exact up to second order in the Coulomb correlation U and reproduces the atomic limit-is used for the effective SIAM. To include the scattering by the impurities we use the coherent potential approximation (CPA) which is consistent with the DMFT. For various concentrations c of the impurities we calculate the resistivity as well as the thermoelectrical power in a situation describing a Kondo insulator in the pure case (c = 0). (c) 2005 Elsevier B.V. All rights reserved.