Abstract The body-centered cubic Pu 2C 3-type structure of yttrium sesquicarbide, Y 2C 3, has been prepared in high yield by high pressure-high temperature techniques. Lattice parameter measurements indicate a homogeneity range for the compound. Magnetic susceptibility measurements show the material is superconducting over the entire homogeneity range with the superconducting transition temperature varying from a low of 6.0 °K to a high of 11.5 °K. High temperature-ambient pressure annealing of samples prepared by the high pressure-high temperature techniques destroyed the Pu 2C 3-type structure. No superconducting transition was observed on the annealed samples for measurements down to 2.0 °K.