Bulk superconductivity at 10 K in the layered compounds Y2C2I2 and Y2C2Br2

Resistivity, susceptibility, and specific heat measurements on the new layered superconductors Y2C2I2 and Y2C2Br2 have been performed to characterize their superconducting state. Our experiments indicate bulk super conductivity with T-c=9.97 K for Y2C2I2 and T-c=5.04 K for Y2C2Br2. An analysis of the specific heat anomalies at T-c in terms of the weak coupling BCS and the two-fluid model, as well as estimates based on McMillan's formula, reveals strong electron-phonon coupling in the present systems, in contrast to the related three-dimensional superconductor YC2 with T-c approximate to 4.0 K.