  In Uranium-based heavy fermion system, the 5f electrons display an
intermediate character between partial localization and partial itinerancy,
which makes the Kondo problem more complicated. Here we use scanning tunneling
microscopy/spectroscopy to investigate the (001) surface of the Kondo lattice
antiferromagnet USb2. Temperature-dependent dI/dV spectra from 4.7 K up to 140
K reveal several peak structures around the Fermi level. Two pronounced peaks
are originated from the hybridization between the conduction and 5f electrons.
We did not observe the mysteriously abrupt change of the electronic state at 45
K, which is previously reported by another STM group and attributed to a novel
first-order like transition. Instead, we only observe continuous evolution of
the dI/dV spectra with temperature. Furthermore, in some scanning regions, we
find significant Sb atoms missing from the top layer, which gives us the
opportunity to investigate the electronic structure of the U-terminated
surface. For the U-terminated surface, an additional sharp peak emerges, which
is closely related to the magnetic order.
