Specific heat of Mg11B2

We report specific-heat measurements on two samples of (MgB2)-B-11, one powder and one sintered, that give essentially identical results. Both samples are of exceptionally high quality: At the critical temperature the discontinuity in specific heat is higher than that of other samples, the transition is sharper than for most samples, and the signature feature of the small, non-BCS energy gap is particularly pronounced. The results art! compared with a phenomenological model for a multi-gap superconductor, with band-structure calculations, and with spectroscopic determinations of the energy gaps. (C) 2002 Elsevier Science B.V. All rights reserved.