  We investigate the magnetothermodynamic properties of the perovskite
manganite Pr0.46Sr0.54MnO3. Our data imply that the paramagnetic to
antiferromagnetic transition at TN = 210 K is first order with an abrupt
decrease of volume (~ 0.14 % in zero magnetic field) and is accompanied by a
sharp anomaly in specific heat. Upon application of a sufficiently large
magnetic field, the antiferromagnetic phase transforms into a ferromagnetic
phase with a sharp increase in sample volume. This field induced transition
results in a large positive magnetocaloric effect just below TN (&#8710;Sm =
10.4 Jkg-1K-1 at H = 5.5 T), which is associated with the increasing stability
of the antiferromagnetic state with decreasing temperature.
