  Synthesis of a series of layered iron arsenides Ca1-xRExFeAs2 (112) was
attempted by heating at 1000 C under a high-pressure of 2 GPa. The 112 phase
successfully forms with RE = La, Ce, Nd, Sm, Eu and Gd, while Tb, Dy and Ho
substituted and RE free samples does not contain the 112 phase. The Ce, Nd, Sm,
Eu and Gd doped Ca1-xRExFeAs2 are new compounds. All of them exhibit
superconducting transition except for the Ce doped sample. The behaviour of the
critical temperature, with the RE ionic radii have been investigated.
