  Superconducting properties of Co-co-doped (Ca,RE)FeAs2 ((Ca,RE)112: RE = La,
Pr) were investigated. Co-co-doping increased Tc of (Ca,Pr)112 while
Mn-co-doping suppressed superconductivity of (Ca,RE)112. Co-co-doped (Ca,La)112
showed large diamagnetic screening and sharper superconducting transition than
Co-free (Ca,La)112. Tczero observed in resistivity measurements increased from
14 K to 30 K by Co-co-doping, while Tconset was not increased. The critical
current density (Jc) of Co-co-doped (Ca,La)112 were approximately 2.1 x 104
Acm-2 and 3.2 x 103 Acm-2 at 2 K and 25 K, respectively, near zero field. These
relatively high Jcs and large diamagnetic screening observed in susceptibility
measurement as for polycrystalline bulks suggest bulk superconductivity of
Co-co-doped (Ca,RE)112 compounds.
