An unpolarized hydrogenlike atom in the metastable $2{S}_{\frac{1}{2}}$ state in an electric field decays primarily by one- or two-photon emission. The angular distribution of the single-photon radiation is expected to be asymmetric with respect to the electric field direction as a result of $E1\ensuremath{-}M1$ interference. Observable consequences of this effect in high-$Z$ Lamb-shift experiments in progress are pointed out. A lowest-order estimate is given for the dependence of the asymmetry on the nuclear charge and the applied field strength.