Tau Decays Into Three Charged Leptons And Two Neutrinos

We have searched for the radiative leptonic tau decays[tau][yields] ee[sup+]e[sup -][nu][sub[tau]][nu][sub e] and[tau][yields][mu]e[sup+]e[sup -][nu][sub[tau]][nu][sub[mu]] using 3.60 fb[sup -1] of data collected by the CLEO-II experiment at CESR. We present a first observation of the[tau][yields] ee[sup+]e[sup -][nu][sub[tau]][nu][sub e] process. For this channel we measure the branching fraction B([tau][yields] ee[sup+]e[sup -][nu][sub[tau]][nu][sub e])= (2.8[+-] 1.4[+-] 0.4) x 10[sup -5]. An upper limit is established for the second channel: B([tau][yields][mu]e[sup+][nu][sub[tau]][nu][sub[mu]])