  This paper reports specific-heat measurements on superconducting MgB2 in
magnetic fields to 9 T. In zero magnetic field the data can be fitted to a
two-gap model, which is a generalization of a semi-empirical model for
strong-coupled, single-gap superconductors (the alpha-model), to within the
precision of the data. Both gaps close at Tc, with one gap larger and one
smaller than the BCS weak-coupling-limit. (The two gaps have a ratio ~ 4:1.)
Each gap accounts for ~ 50% of the normal electron density of states. The
parameters characterizing the fits agree well with those from recent
spectroscopic measurements and theory. In magnetic fields the superconductong
anomaly is broadened as expected for an anisotropic, randomly-oriented
superconductor.
