With co-refinement of 11-BM X-ray diffraction and POWGEN neutron diffraction data for a sample, the composition of the new ternary phase was refined to Ni 3.9945 V 3.0055 O 10 (Ni and V esd = ± 0.0022). The co-refinement presented no evidence of oxygen vacancies. It is assumed here that the composition is Ni 4 V 3 O 10 . EDS point measurements corroborating this Ni:V ratio are presented in the Supporting Information. 35