Thermopower of an intermediate valence model of Tl2Mn2O7

In this work we calculate the thermopower of Tl2Mn2O7, together with its static resistivity and dynamical conductivity. This compound exhibits colossal magneto resistance, which is not adequately explained by the double-exchange mechanism. We use Hubbard operators to reformulate a previous model of Ventura and Alascio that describes the 3d orbitals of Mn with two magnetic configurations, hybridized with a conduction band associated to the Tl. We reformulate a previous treatment to obtain approximate one-electron green's functions (GF) for the model. We have employed these GF to calculate the properties mentioned above for several values of the system parameters and obtained a qualitative agreement with the experimental results. (C) 2004 Elsevier B.V. All rights reserved.