Crystal structure assignment for the heavy-fermion superconductor $\mathrm{U}{\mathrm{Pt}}_3$

Understanding the normal and superconducting states in ${\mathrm{UPt}}_3$ depends critically on its crystal structure. Based on high-energy x-ray diffraction and transmission electron microscopy, we have determined that the crystal structure of ${\mathrm{UPt}}_3$ is trigonal, not hexagonal as traditionally held. Its trigonal structure provides an interpretation of recent high-field muon spin rotation experiments and may be relevant to the existence of the symmetry-breaking field required by most theoretical models of heavy-fermion superconductivity.