Decays of beauty baryons to the D(0)ph(-) and Lambda(+)(c)h(-) final states (where h indicates a pion or a kaon) are studied using a data sample of pp collisions, corresponding to an integrated luminosity of 1.0 fb(-1), collected by the LHCb detector. The Cabibbo-suppressed decays Lambda(0)(b)-> D(0)pK(-) and Lambda(0)(b)->Lambda K-c(-) are observed, and their branching fractions are measured with respect to the decays Lambda(0)(b)-> D(0)p pi(-) and Lambda(0)(b)->Lambda(+)(c)pi(-). In addition, the first observation is reported of the decay of the neutral beauty-strange baryon Xi(0)(b) to the D(0)pK(-)final state, and a measurement of the Xi(0)(b) mass is performed. Evidence of the Xi(0)(b)->Lambda K-c(-) decay is also reported.