Reduction of the low-temperature bulk gap in samarium hexaboride under   high magnetic fields
  SmB$_6$ exhibits a small (15-20 meV) bandgap at low temperatures due to hybridized $d$ and $f$ electrons, a tiny (3 meV) transport activation energy $(E_{A})$ above 4 K, and surface states accessible to transport below 2 K. We study its magnetoresistance in 60-T pulsed fields between 1.5 K and 4 K. The response of the nearly $T$-independent surface states (which show no Shubnikov-de Haas oscillations) is distinct from that of the activated bulk. $E_{A}$ shrinks by 50% under fields up to 60 T. Data up to 93 T suggest that this trend continues beyond 100 T, in contrast with previous explanations. It rules out emerging theories to explain observed exotic magnetic quantum oscillations. 
S. Wolgast, Y. S. Eo, K. Sun, \c{C}. Kurdak, F. F. Balakirev, M.   Jaime, D.-J. Kim, and Z. Fisk
cond-mat.str-el