Stark effect for a difference Schrödinger operator

The tight-binding model of electron motion in an uniform electric field is considered and the spectrum of the corresponding Schrödinger operator perturbed by the potential of an ideal crystallic lattice or the potential rapidly decreasing at infinity. It is shown that for typical directions of the stress vector of the electric field with respect to the basis vectors of the lattice the Schrodinger operator has the purely point and everywhere dense spectrum if the perturbations are small.