Searches for B mesons decaying to final states containing a baryon and a lepton are performed, where the baryon is either Λ c or Λ and the lepton is a muon or an electron. These decays violate both baryon and lepton number and would be a signature of physics beyond the standard model. No significant signal is observed in any of the decay modes, and upper limits in the range ( 3.2 - 520 ) × 10 − 8 are set on the branching fractions at the 90% confidence level.