  We calculate the thermal conductivity of interacting electrons in disordered
metals. In our analysis we point out that the interaction affects thermal
transport through two distinct mechanims, associated with quantum interference
corrections and energy exchange of the quasi particles with the electromagnetic
environment, respectively. The latter is seen to lead to a violation of the
Wiedemann-Franz law. Our theory predicts a strong enhancement of the Lorenz
ratio $\kappa /\sigma T$ over the value which is predicted by the
Wiedemann-Franz law, when the electrons encounter a large environmental
impedance.
