  We report the observation of the baryonic B-decay B0bar -> Lambda_c^+
antiproton K^- pi^+, excluding contributions from the decay B0bar -> Lambda_c^+
anti-Lambda K^-. Using a data sample of 467*10^6 BBbar pairs collected with the
BABAR detector at the PEP-II storage ring at SLAC, the measured branching
fraction is (4.33 +/- 0.82_stat +/- 0.33_syst +/- 1.13_Lambda_c^+)*10^-5. In
addition we find evidence for the resonant decay B0bar -> Sigma_c(2455)^++
antiproton K^- and determine its branching fraction to be (1.11 +/- 0.30_stat
+/- 0.09_syst +/- 0.29_Lambda_c^+)*10^-5. The errors are statistical,
systematic, and due to the uncertainty in the Lambda_c^+ branching fraction.
For the resonant decay B0bar -> Lambda_c^+ antiproton K^*0 we obtain an upper
limit of 2.42*10^-5 at 90% confidence level.
