Topological insulators, with metallic boundary states protected against time-reversal-invariant perturbations, are a promising avenue for realizing exotic quantum states of matter including various excitations of collective modes predicted in particle physics, such as Majorana fermions and axions. According to theoretical predictions, a topological insulating state can emerge from not only a weakly interacting system with strong spin-orbit coupling, but also in insulators driven by strong electron correlations. The Kondo insulator compound SmB6 is an ideal candidate for realizing this exotic state of matter, with hybridization between itinerant conduction electrons and localized $f$-electrons driving an insulating gap and metallic surface states at low temperatures. Here we exploit the existence of surface ferromagnetism in SmB6 to investigate the topological nature of metallic surface states by studying magnetotransport properties at very low temperatures. We find evidence of one-dimensional surface transport with a quantized conductance value of $e^2/h$ originating from the chiral edge channels of ferromagnetic domain walls, providing strong evidence that topologically non-trivial surface states exist in SmB6.
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