  The specific heat $C(T)$ of BaFe$_2$As$_2$ single crystal, electron-doped
Ba$_{0.7}$La$_{0.3}$Fe$_2$As$_2$ and hole-doped Ba$_{0.5}$K$_{0.5}$Fe$_2$As$_2$
polycrystals were measured. For undoped BaFe$_2$As$_2$ single crystal, a very
sharp specific heat peak was observed at 136 K. This is attributed to the
structural and antiferromagnetic transitions occurring at the same temperature.
$C(T)$ of the electron-doped non-superconducting
Ba$_{0.7}$La$_{0.3}$Fe$_2$As$_2$ also shows a small peak at 120 K, indicating a
similar but weaker structural/antiferromagnetic transition. For the hole-doped
superconducting Ba$_{0.5}$K$_{0.5}$Fe$_2$As$_2$, a clear peak of $C/T$ was
observed at $T_c$ = 36 K, which is the highest peak seen at superconducting
transition for iron-based high-$T_c$ superconductors so far. The electronic
specific heat coefficient $\gamma$ and Debye temperature $\Theta_D$ of these
compounds were obtained from the low temperature data.

Superconductivity;Strongly Correlated Electrons