Evidence for penguin-diagram decays: First observation of [ital B][r arrow][ital K][sup *](892)[gamma]

We have observed the decays [ital B][sup 0][r arrow][ital K][sup *](892)[sup 0][gamma] and [ital B][sup [minus]][r arrow][ital K][sup *](892)[sup [minus]][gamma], which are evidence for the quark-level process [ital b][r arrow][ital s][gamma]. The average branching fraction is (4.5[plus minus]1.5[plus minus]0.9)[times]10[sup [minus]5]. This value is consistent with standard model predictions from electromagnetic penguin diagrams.