Hidden Phase in UBiTe Studied by Scanning Tunneling Spectroscopy

Actinide compounds have attracted considerable interest in recent years because of the interaction between magnetism, heavy fermions, and other order parameters, such as in the spin-triplet superconductor UTe₂ or the hidden-order system URu₂Si₂. Using scanning tunneling microscopy and spectroscopy (STM/S), we investigate the uranium-based Kondo lattice ferromagnet UBiTe. Due to the weak interlayer coupling in this material, we are able to study several different surface terminations, allowing us to observe how changes in the density of states appear below approximately 3 K on multiple surfaces. On the Te surface, we uncover a previously unreported phase which opens a gap in the density of states. We also observe a series of peaks in the density of states on the U surface in the same temperature range.