  First quasiclassical correction to the differential cross section of
high-energy electron-positron photoproduction in the electric field of a heavy
atom is obtained with the exact account of the field. This correction is
responsible for the charge asymmetry ${\cal A}$ in this process. When the
transverse momentum of at least one of the produced particles is much larger
than the electron mass $m$, the charge asymmetry can be as large as tens
percent. We also estimate the contribution $\tilde{\cal A}$ to the charge
asymmetry coming from the Compton-type diagram. For heavy nuclei, this
contribution is negligible. For light nuclei, $\tilde{\cal A}$ is noticeable
only when the angle between the momenta of electron and positron is of order of
$m/\omega$ ($\omega$ is the photon energy) while the transverse momenta of both
particles are much larger than $m$.
