A search for the rare two-body decays b D° and b° D° is performed with proton-proton collision data, collected by the LHCb experiment at a center-of-mass energy of 13 TeV. The decay b D° is seen with a statistical significance of 5.5 standard deviations and constitutes the discovery for this decay. An excess of b° D° candidates w.r.t. the background is observed with a statistical significance of 1.8 standard deviations.<eng>
