We report results from a study of events with a leading antiproton of beam
momentum fraction 0.905 < x(F) < 0.965 and 4-momentum transfer squared \t\
< 3 GeV2 produced in (p) over bar p collisions at root s = 1800 GeV at the
Fermilab Tevatron collider. Approximately 2% of the events contain two jets
of transverse energy E-T(jet) > 7 GeV. Using the dijet events, we evaluate
the diffractive structure function of the antiproton and compare it with e
xpectations based on results obtained in diffractive deep inelastic scatter
ing experiments at the DESY cp collider HERA.