Direct Observation of Coexisting Kondo Hybridization and Antiferromagnetic State in UAs2

In f-electron heavy fermion systems, a wide variety of fascinating magnetic and electronic properties arise, and they are often thought to be related to a crossover behavior between localized and itinerant regimes for f electrons. Uranium-based compounds with partially occupied 5 f orbitals provide an ideal platform to elucidate the outstanding issue of the competition between magnetic order and Kondo entanglement. Using angle-resolved photoemission spectroscopy, complemented by density functional theory simulations, we probe the temperature-dependent evolution of the low-energy electronic structure of UAs2 and observe two nearly flat bands of different origin in the antiferromagnetic (AFM) state. A nearly flat band which behaves with quasi-two-dimensional character has been observed and contributed to the heavy spectral weight at the gamma point around E-F. This flat band reveals typical Kondo hybridization. Another flat band around the M point is closely related to paramagnetic (PM)-AFM phase transition, which opens an energy gap below the transition temperature & SIM;273 K. Our results provide direct spectral demonstration of the electronic structure evolution across the f-c hybridization and PM-AFM transition in UAs2.