ABSTRACT The Kondo lattice system is a unique member among the hexaborides due to its multi‐phase magnetic phase diagram, dense Kondo behavior, and antiferroquadrupolar ordering. Understanding its surface properties is crucial for interpreting the results of highly surface‐sensitive techniques like Scanning Tunneling Microscopy (STM) and angle‐resolved photoemission spectroscopy (ARPES). In this study, we conducted a comprehensive survey of surfaces prepared by low‐temperature in situ cleaving and investigated by low‐temperature STM. Two different types of surface reconstructions could be located, but atomically flat, non‐reconstructed surface areas could be found only very rarely and were limited in size to a few tens of nanometers. Tunneling spectroscopic measurements within such non‐reconstructed clean areas revealed a partially opened gap of about 42 meV at 4.6 K. Its origin is discussed to rely either on Kondo hybridization or on strong correlation effects in the 5–2 band structure. Density functional theory (DFT) calculations show that the common wide bands of itinerant 5 and 2 electrons remain robust for bulk . Spectra obtained on reconstructed surfaces indicated a modified low‐energy electronic surface structure. Our work draws attention to the impact of details of the surface structure of complex materials like on its electronic surface properties.
Crivillero et al. (Sun,) studied this question.