  We have succeeded in growing single crystals of the heavy-fermion
superconductor CeCo(In1-xZnx)5 with x<=0.07. Measurements of specific heat,
electrical resistivity, dc magnetization and ac susceptibility revealed that
the superconducting (SC) transition temperature Tc decreases from 2.25 K (x=0)
to 1.8 K (x=0.05) by doping Zn into CeCoIn5. Furthermore, these measurements
indicate a development of a new ordered phase below T_o ~ 2.2 K for x=>0.05,
characterized by the reduced magnetization and electrical resistivity in the
ordered phase, and the enhancement of specific heat at T_o. This phase
transition can be also recognized by the shoulder-like anomaly seen at H_o ~ 55
kOe in the field variations of the magnetization at low temperatures, which is
clearly distinguished from the superconducting critical fields Hc2=49 kOe for
x=0.05 and 42 kOe for x=0.07. We suggest from these results that the
antiferromagnetic (AFM) order is generated by doping Zn, and the interplay
between the SC and AFM orders is realized in CeCo(In1-xZnx)5.
