  The Lorenz ratio serves as a measure to compare thermal and electric
conductivities of metals. Recent experiments observed small Lorenz ratios in
the compensated metal WP$_2$, indicating that charge flow is strongly favored
over heat conduction. Motivated by these findings, we study transport
properties of compensated metals in the presence of electron-electron
collisions and electron-impurity scattering. We focus on intermediate
temperatures, where the phonon contributions to transport are weak and elastic
and inelastic scattering rates are comparable. Our exact solution for the
kinetic equation in the presence of general Fermi-liquid interactions is used
to extract the Lorenz ratio for short and long range interactions. We find that
the Lorenz ratio develops a temperature dependence and gets enhanced as a
consequence of disorder scattering. For collisions mediated by the Coulomb
interaction, impurities give rise to a non-monotonic dependence of the Lorenz
ratio on the screening wave number with a minimum for intermediate screening
strength. To help future experimental efforts, we establish a scheme to connect
the exact results with the solution of the Boltzmann equation under the
relaxation time approximation for all collision integrals. Our recipe provides
simple phenomenological expressions for the transport coefficients and it
allows for a physically transparent interpretation of the results.
