  We study the $\bar D D$ (${\bar D}^0 D^0$ and $D^-D^+$) charm meson pair
production in antiproton (${\bar p}$) induced reactions on nuclei at beam
energies ranging from threshold to several GeV. Our model is based on an
effective Lagrangian approach that has only the baryon-meson degrees of freedom
and involves the physical hadron masses. The reaction proceeds via the
$t$-channel exchanges of $\Lambda_c^+$, $\Sigma_c^+$, and $\Sigma_c^{++}$
baryons in the initial collision of the antiproton with one of the protons of
the target nucleus. The medium effects on the exchanged baryons are included by
incorporating in the corresponding propagators, the effective charm baryon
masses calculated within a quark-meson coupling (QMC) model. The wave functions
of the bound proton have been determined within the QMC model as well as in a
phenomenological model where they are obtained by solving the Dirac equation
with appropriate scalar and vector potentials. The initial- and final-state
distortion effects have been approximated by using an eikonal
approximation-based procedure. Detailed numerical results are presented for
total and double differential cross sections for the ${\bar D}^0 D^0$ and
$D^-D^+$ production reactions on $^{16}$O and $^{90}$Zr targets. It is noticed
that at ${\bar p}$ beam momenta of interest to the ${\bar P}ANDA$ experiment,
medium effects lead to noticeable enhancements in the charm meson production
cross sections.
