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 cha racterize their superconducting state. Our experiments indicate bulk s uper conductivity with T-c=9.97 K for Y2C2I2 and T-c=5.04 K for Y2C2Br 2. An analysis of the specific heat anomalies at T-c in terms of the w eak coupling BCS and the two-fluid model, as well as estimates based o n McMillan's formula, reveals strong electron-phonon coupling in the p resent systems, in contrast to the related three-dimensional supercond uctor YC2 with T-c approximate to 4.0 K.