Ferromagnetism and heavy fermion semiconductor-like behavior in UFe0.6Sb2 single crystals

• Single crystals of UFe0.6Sb2 were prepared by self-flux method.
• UFe0.6Sb2 has a ferromagnetic-type transition at 28 K.
• Heavy fermion semiconductor-like behavior in UFe0.6Sb2 was confirmed.
• One pseudogap can be closed by applying high magnetic field.
• Large electronic specific heat coefficient indicates that UFe0.6Sb2 is a strong electron correlation material.

Single crystals of UFe0.6Sb2 grown by Sb flux method have been investigated by means of X-ray diffraction, magnetic susceptibility, electrical resistivity and specific heat. UFe0.6Sb2 crystallizes in the tetragonal HfCuSi2-type structure (space group P4/nmm). UFe0.6Sb2 undergoes a ferromagnetic transition at TC = 28 K with an easy axis along the c-axis. The resistivity resembles heavy fermion semiconducting-like behavior and implies three pseudogaps are formed in both directions. One pseudogap formed in the range of 9–30 K originates from states of impurity due to the partial occupancies of the Fe sites, and it can be closed by applying high magnetic field. The magnetic field, however, has little effects on the other two pseudogaps. A large electronic specific heat coefficient γ = 233 mJ/mol·K2 reveals this compound is a strong electron correlation material.