  We study the semiclassical dynamics of interacting electrons in a biased
crystal lattice. A complex dynamical scenario emerges from the interplay
between the Coulomb and the external electric fields. When the electrons are
far apart, the Coulomb potential may be small compared to the external
potential and the electrons oscillate with effective Bloch frequencies,
determined by the local electric field. In the opposite case, nearby electrons
either separate or form a bound pair, depending on the initial energy compared
to the band width. The pair due to the Coulomb field is stable even in the
absence of the external field.
