  D. J. Antonio et al. report an x-ray diffraction experiment on uranium
dioxide at high-magnetic field and low temperature. The authors have apparently
not realized that the diffraction data actually shows unambiguously the
presence of a rhombohedral distortion induced by the field at low temperature
and the presence of more than one domain. Our note correctly analyses their
data. The crystallographic analysis we perform is based on simple arguments
with respect to plane spacings in slightly distorted cubic materials. Similar
studies have been reported in many materials over the last 50 years. Our
analysis explains quantitatively the observations, the presence of the two
peaks (the appearance of which the authors regard as unexpected) and their
different variations with respect to the applied field, which is a simple
consequence of the conservation of atomic volume.
