  We investigate the temperature dependence of the resistivity and
magnetoresistance of a polycrystalline $Sr_2CoMoO_{6-\delta}$ film deposited on
(100)-$SrTiO_3$ substrate prepared by the pulsed laser deposition method. X-ray
diffraction, Raman and magnetoresistance results demonstrate clearly the
coexistence of a ferromagnetic metallic and an antiferromagnetic (or
paramagnetic) insulating domain. Percolative transition between these two
phases as the temperature varies, which is believed to induce a metal-insulator
transition at around $T_C$, has been directly observed in our measurements of
the temperature dependence of the sample resistivity. Thus we have provided new
direct evidence that a phase separation scenario also exists in the ordered
double-perovskite structure materials.
