%0 Journal Article %T Heat Capacity of MgB_2: Evidence for Moderately Strong Coupling Behavior %A R. K. Kremer %A B. J. Gibson %A K. Ahn %J Physics %D 2001 %I arXiv %X We characterize the superconducting state of phase pure polycrystalline samples of the new layered superconductor MgB$_2$ by specific heat measurements in magnetic fields up to 9 T. The characteristic jump at the superconducting transition is observed and compared with the predictions of weak coupling BCS-theory and the $\alpha$-model. Our analysis shows excellent agreement with the predictions for 2$\Delta/k_BT_{\rm C}$ = 4.2(2) with a Sommerfeld term $\gamma_{\rm exp}$ of 3.1(1) mJ/mol K$^2$ indicating that MgB$_2$ is a superconductor in the moderately strong electron-phonon coupling regime. %U http://arxiv.org/abs/cond-mat/0102432v2