  It is argued that the experimentally observed baryon stopping may indicate
(within the present experimental uncertainties) a non-monotonous behaviour as a
function of the incident energy of colliding nuclei. This can be quantified by
a midrapidity reduced curvature of the net-proton rapidity spectrum. The above
non-monotonous behaviour reveals itself as a "zig-zag" irregularity in the
excitation function of this curvature. The three-fluid dynamic calculations
with a hadronic equation of state (EoS) fail to reproduce this irregularity. At
the same time, the same calculations with an EoS involving a first-order phase
transition into the quark-gluon phase do reproduce this "zig-zag" behaviour,
however only qualitatively.
