Observation of Kondo lattice behavior in antiferromagnetic metal FeTe

Finding d-electron heavy fermion (HF) states has been an important topic as the diversity in d-electron materials can lead to many exotic Kondo effect-related phenomena or new states of matter such as topological Kondo insulator. Yet, obtaining direct spectroscopic evidence for a d-electron HF system has been elusive to date. Here, we report the observation of Kondo lattice behavior in an antiferromagnetic metal, FeTe, via angle-resolved photoemission spectroscopy (ARPES) and transport properties measurements. The Kondo lattice behavior is represented by the emergence of a sharp quasiparticle at low temperatures. The transport property measurements confirm the low-temperature Fermi liquid behavior and reveal successive coherent-incoherent crossover upon increasing temperature. It is also found that the low-temperature coherent state of the Kondo lattice is facilitated by a long-range magnetism. We interpret the Kondo lattice behavior as a result of hybridization between localized Fe 3d_xy and itinerant Te 5p_z orbitals. Our observations suggest unusual cooperation of Kondo lattice behavior and long-range magnetism.