The Λb0→Λc+K+K−π− decay is observed for the first time using a data sample of proton-proton collisions at centre-of-mass energies of s=7 and 8TeV collected by the LHCb detector, corresponding to an integrated luminosity of 3fb−1. The ratio of branching fractions between the Λb0→Λc+K+K−π− and the Λb0→Λc+Ds− decays is measured to be [Formula presented] where the first uncertainty is statistical, the second systematic and the third is due to the knowledge of the Ds−→K+K−π− branching fraction. No structure on the invariant mass distribution of the Λc+K+ system is found, consistent with no open-charm pentaquark signature.
