Photoemission signature of the competition between magnetic order and Kondo effect in CeCoGe3

The competition between magnetic order and Kondo effect is essential for the rich physics of heavy fermion systems. Nevertheless, how such competition is manifested in the quasiparticle bands in a real periodic lattice remains elusive in spectroscopic experiments. Here we report a high-resolution photoemission study of the antiferromagnetic Kondo lattice system CeCoGe3 with a high TN1 of 21 K. Our measurements reveal a weakly dispersive 4 f band at the Fermi level near the Z point, arising from a moderate Kondo effect. The intensity of this heavy 4 f band exhibits a logarithmic increase with lowering temperature and begins to deviate from this Kondo-like behavior below -25 K, just above TN1, and eventually ceases to grow below -12 K. Our work provides direct spectroscopic evidence for the competition between magnetic order and the Kondo effect in a Kondo lattice system with local-moment antiferromagnetism, indicating a distinct scenario for the microscopic coexistence and competition of these phenomena, which might be related to the real-space modulation.