  Uranium ions in sesquinitride alpha-U2N3 occupy independent acentric and
centrosymmetric sites according to conventional x-ray diffraction patterns [R.
Tro\'c, J. Solid State Chem. 13, 14 (1975)]. We submit that polar uranium
multipoles in acentric sites are revealed in resonant x-ray diffraction data
recently published by Lawrence Bright et al. [Phys. Rev. B 100, 134426 (2019)].
To this end, their diffraction data gathered with a primary x-ray energy in the
vicinity of the uranium M4 absorption edge are compared to symmetry-informed
diffraction amplitudes calculated for the bixbyite alpha-Mn2O3 lattice
structure. Bragg spots forbidden in this lattice diffraction pattern appear to
provide clear-cut evidence for high-order polar uranium multipoles.
