  Recently, the resistance saturation at low temperature in Kondo insulator
SmB6, a long-standing puzzle in condensed matter physics, was proposed to
originate from topological surface state. Here,we systematically studied the
magnetoresistance of SmB6 at low temperature up to 55 Tesla. Both temperature-
and angular-dependent magnetoresistances show a similar crossover behavior
below 5 K. Furthermore, the angular-dependent magnetoresistance on different
crystal face confirms a two-dimensional surface state as the origin of
magnetoresistances crossover below 5K. Based on two-channels model consisting
of both surface and bulk states, the field-dependence of bulk gap with critical
magnetic field (Hc) of 196 T is extracted from our temperature-dependent
resistance under different magnetic fields. Our results give a consistent
picture to understand the low-temperature transport behavior in SmB6,
consistent with topological Kondo insulator scenario.
