Single crystal neutron diffraction determination of U6Fe Structure

U6Fe is an interesting superconductor with an exceptionally high critical field of 12 T and a superconducting transition temperature of 4K, the highest known for a uranium-based heavy-fermion superconductor, where neither the Pauli nor usual BCS orbital limit is apparently respected. Previous studies of bulk U6Fe provide evidence that the material may undergo a change or possible phase transition at around 110 K, while X-rays showed a CDW that appeared below 10 K. The interplay between CDW order and superconductivity is highly topical, both in the context of heavy fermions but also for high-temperature superconductivity. For U6Fe a CDW may promote the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, an unusual state in which the superconducting order parameter is modulated in real space. Previous neutron measurements showed the presence of disallowed nuclear Bragg peaks, suggesting the previously-reported crystal structure may be incomplete. We propose to measure the crystal strcutre of U6Fe at various temperatures to determine the nature of the crystal structure and how it may be affected by the phase transitions at 110K and 10K.