  Magnetic structure of the multiferroic Ca$_{2}$CoSi$_{2}$O$_{7}$ was
determined by neutron diffraction techniques. Combination of the
polycrystalline and single-crystal samples experiments revealed a collinear
antiferromagnetic structure with the easy axis along $<$100$>$ directions. The
dielectric state was discussed in the framework of the spin-dependent $d$-$p$
hybridization mechanism, leading to the realization of the antiferroelectric
structure. The origin of the magnetic anisotropy was discussed in comparison
with the isostructural Ba$_{2}$CoGe$_{2}$O$_{7}$.
