We report on the magnetic and superconducting properties of single crystals of the alloys CeRh_1-xCo_xIn₅ (x = 0.0, 0.25, 0.5, 1.0). For x \leq 0.5 we do not find any signature of superconductivity down to 1.6 K. The previously observed metamagnetic transition in CeRhIn₅ at 20 kOe is also present for small Co doping (x = 0.25), but disappears for x = 0.5. In the superconducting state, CeCoIn₅ shows hysteresis in the magnetisation versus field measurements which is typical of a type II superconductor, with the pinning predominantly controlled by surface and geometrical factors.

PACS numbers: 71.27.+a, 74.70.Tx, 74.60.Ge