Abstract
The heat capacity of several sintered specimens of YBa2Cu3O7-y, the high-temperature superconductor, has been measured from 1.5 to 10 K in magnetic fields up to 4.5 T. Part of the low-temperature anomaly in the heat capacity is ascribed to very small concentrations of localised Cu++ spins. There is a dependence of heat capacity on field which is consistent with a contribution from the electrons in flux-line cores but other features of the results are not yet understood.