  The transverse mass distributions for antiprotons are measured at midrapidity
for minimum bias Pb+Pb collisions at 158A GeV and for central Pb+Pb collisions
at 20A, 30A, 40A and 80A GeV beam energies in the fixed target experiment NA49
at the CERN SPS. The rapidity density, inverse slope parameter and mean
transverse mass derived from the transverse mass distributions are studied as a
function of the incident energy and the collision centrality and compared to
the relevant data on proton production. The shapes of the transverse mass
distributions of antiproton and proton are very similar. The ratios of the
particle yields, antiproton/proton and antilambda/antiproton, are also
analysed. The antiproton to proton ratio exhibits an increase with decreasing
centrality and a steep rise with increasing beam energy. The antilambda to
antiproton ratio increases beyond unity with decreasing beam energy.
