  Elastic and inelastic neutron scattering measurements have been carried out
to investigate the magnetic properties of superconducting (Tc~8K) HoNi2B2C. The
inelastic measurements reveal that the lowest two crystal field transitions out
of the ground state occurat 11.28(3) and 16.00(2) meV, while the transition of
4.70(9) meV between these two levels is observed at elevated temperatures. The
temperature dependence of the intensities of these transitions is consistent
with both the ground state and these higher levels being magnetic doublets. The
system becomes magnetically long range ordered below 8K, and since this
ordering energy kTN ~ 0.69meV << 11.28meV the magnetic properties in the
ordered phase are dominated by the ground-state spin dynamics only. The low
temperature structure, which coexists with superconductivity, consists of
ferromagnetic sheets of Ho{3+ moments in the a-b plane, with the sheets coupled
antiferromagnetically along the c-axis. The magnetic state that initially forms
on cooling, however, is dominated by an incommensurate spiral antiferromagnetic
state along the c-axis, with wave vector qc ~0.054 A-1, in which these
ferromagnetic sheets are canted from their low temperature antiparallel
configuration by ~17 deg. The intensity for this spiral state reaches a maximum
near the reentrant superconducting transition at ~5K; the spiral state then
collapses at lower temperature in favor of the commensurate antiferromagnetic
state. We have investigated the field dependence of the magnetic order at and
above this reentrant superconducting transition. Initially the field rotates
the powder particles to align the a-b plane along the field direction,
demonstrating that the moments strongly prefer to lie within this plane due to
the crystal field anisotropy. Upon subsequently increasing the field at
