Robust coherence phenomena and surface states in magnetically alloyed SmB6

Samarium hexaboride is a candidate for the topological Kondo insulator state, in which Kondo coherence is predicted to give rise to an insulating gap spanned by topological surface states. Here we investigate the surface and bulk electronic properties of magnetically alloyed Sm1-xMxB6 (M=Ce, Eu). Remarkably, in-gap surface states visible to angle-resolved photoemission spectroscopy (ARPES) and resistivity features associated with Kondo coherence are both found to persist in highly modified samples with up to 30% Sm substitution. The results are interpreted in terms of a hierarchy of energy scales, in which surface state emergence is linked to the relatively robust formation of a direct Kondo gap.