  The behavior of a Bloch particle in a complex crystal with PT symmetry
subjected to a sinusoidal ac force is theoretically investigated. For unbroken
PT symmetry and in the single-band approximation, it is shown that time
reversal symmetry of the ac force preserves the reality of the quasienergy
spectrum. Like in ordinary crystals, exact band collapse, corresponding to
dynamic localization, is attained for a sinusoidal band shape. The wave packet
dynamics turns out to be deeply modified at the PT symmetry breaking point,
where band merging occurs and Bragg scattering in the crystal becomes highly
non-reciprocal.
