  We study a molecular lattice Hamiltonian in which polaronic charge carriers
interact with non linear potentials provided by local atomic fluctuations
between two equilibrium sites. The path integral formalism is applied to select
the class of atomic oscillations which mainly contributes to the partition
function and the electrical resistivity is computed in a number of
representative cases. Non metallic resistivity behaviors are found at
temperatures above $\simeq 100K$.
