  We investigate the angular distribution of positrons in the coherent process
electronpositron pair creation process by high-energy photons in a periodically
deformed single crystal with a complex base. The formula for the corresponding
differential cross-section is derived for an arbitrary deformation field. The
case is considered in detail when the photon enters into the crystal at small
angles with respect to a crystallographic axis. The results of the numerical
calculations are presented for${\mathrm{SiO}}_{2}$ and diamond single crystals
and Moliere parameterization of the screened atomic potentials in the case of
the deformation field generated by the acoustic wave of S-type.
