  Estimates of differential cross sections and longitudinal asymmetries are
presented for the reactions $\bar pp\to \bar \Xi\Xi$ and $\bar pp\to \bar
\Xi_c\Xi_c$ at energies $\sqrt{s}\lesssim 15$ GeV. The $\Xi$ and $\Xi_c$
hyperons are assumed to be produced in two-step processes: first, intermediate
$\bar\Lambda\Lambda$ and/or $\bar\Lambda_c\Lambda_c$ states are created which
are converted afterwards into final states $\bar \Xi\Xi$, $\bar \Xi_c\Xi_c$ and
$\bar \Xi_c\Xi_c$. The full amplitudes are described by loop diagrams within a
modified Regge model, based on the topological decomposition of planar quark
diagrams. A strong sensitivity of the ratio of yields of $\bar \Xi_c\Xi_c$ to
$\bar \Xi\Xi$ and of $\bar \Lambda_c\Lambda_c$ to $\bar \Lambda\Lambda$ to the
degree of SU(4) symmetry violation is found.
