Using data collected with the OPAL detector at LEP, we have searched for the processes e+e−→Z0→pe−,pμ− and the charge conjugate final-states. These would violate the conservation of the baryon-number B, lepton-number L and the fermion-number n = (B+L). No evidence for such decays has been found, and the 95% confidence level upper limits on the partial widths Γ(Z0→pe) and Γ(Z0→pμ) are found to be 4.6 and 4.4 keV respectively.