  A point-like neutron in an external electromagnetic field experiences a shift
in energy that mimicks the effect of an actual structural deformation of an
extended neutron, i.e., a proper polarizability. In order to be able to
differentiate between the former and the latter, a Foldy-Wouthuysen
transformation is constructed which yields the energy shift of a point-like
neutron quadratic in the external field in a derivative expansion, generalizing
a long-known result for the dipole electric polarizability due to Foldy. The
ten leading Foldy contributions to the energy are determined for a
zero-momentum neutron. In addition, eliminating the momentum operator in favor
of the velocity operator, analogous results are derived for a zero-velocity
neutron. In this case, operator ordering ambiguities are encountered that
permit only a determination of eight of the ten Foldy terms.
