  It is shown that under certain dynamical conditions a material wave packet
displays coherent, non-dispersive accelerated evolution in gravitational field
over a modulated atomic mirror. The phenomenon takes place as a consequence of
simultaneous presence of the dynamical localization and the coherent Fermi
acceleration for the same modulation amplitude. It is purely a quantum
mechanical effect as the windows of modulation strengths supporting dynamical
localization and Fermi acceleration overlap for larger effective Plank
constant. Present day experimental techniques make it feasible to realize the
system in laboratory.
