  Using the previously developed model we study the electrocaloric effect (ECE)
in antiferroelectric crystals of squaric acid. At low temperatures, the
polarization reorientation by the electric field applied along the
crystallographic $a$ axis of these crystals is predicted to be a two-stage
process, with one of the sublattice polarizations switched twice, by 90$^\circ$
each time. The $T$-$E$ landscapes of the model polarization and entropy are
explored. The ECE, characterized by the introduced electric Gr\"uneisen
parameter, is found to be negative in the antiferroelectric phase. In the
intermediate ferrielectric phase with perpendicular sublattice polarizations it
is positive at low fields, but becomes slightly negative below the transition
to the ferroelectric phase. In the ferroelectric phase the ECE is positive at
all temperatures and fields. Maximal EC temperature shift magnitude is
predicted to be just less than -3 K at 200 kV/cm. The supercritical behavior of
the Gr\"uneisen parameter in the crossover region between two bicritical end
points is explored.
