  Using the previously developed model we explore the processes of polarization
rotation in antiferroelectric crystals of squaric acid by the electric fields
directed arbitrarily within the $ac$ plane. Except for some particular
directions of the field, the two-step polarization reorientation at low
temperatures is predicted: first, to the noncollinear phase with perpendicular
sublattice polarizations and then to the collinear ferroelectric phase.
However, when the field is directed along the axis of spontaneous sublattice
polarizations, the intermediate noncollinear phase is absent; when the field is
at 45$^\circ$ to this axis, the field for transition to the ferroelectric phase
tends to infinity. The ground state proton configurations and the directions of
the sublattice polarization vectors are determined for all field orientations.
The $T$-$E$ phase diagrams are constructed for the fields directed along the
diagonals of the $ac$ plane and for the above discussed particular directions
of the field.
