Electroweak radiative corrections toH+→tb¯for a heavy top quark

The electroweak corrections arising from $t$-quark loop and Higgs loop diagrams to the tree-level process $H^{+}\to t\overline{b}$ are calculated in the minimal supersymmetric standard model. Taking into account the additional contributions to $\Delta r$ arising from the heavy Higgs loops, we present the results in both the $G_F$ scheme and the $\alpha$ scheme.