We report on a search for charge−1/3 third-generation leptoquarks (LQ) produced in p¯p collisions at √s=1.8TeV using the D0 detector at Fermilab. Third-generation leptoquarks are assumed to be produced in pairs and to decay to a tau neutrino and a b quark with branching fraction B. We place upper limits on σ(p¯p→LQ¯LQ)B2 as a function of the leptoquark mass MLQ. Assuming B=1, we exclude at the 95% confidence level third-generation scalar leptoquarks with MLQ<94GeV/c2, and third-generation vector leptoquarks with MLQ<216GeV/c2(MLQ<148GeV/c2) assuming Yang-Mills (anomalous) coupling.Received 10 March 1998DOI:https://doi.org/10.1103/PhysRevLett.81.38©1998 American Physical Society