We have studied the energy gap of the intermediate valent small-gap semicon
ductor SmB6 by means of electrical resistivity measurements. The data recei
ved from the investigation of three single-crystalline samples have shown t
hat at lowest temperatures the resistivity exhibits an activated behaviour
with an energy gap of a few mK. The structure and origin of the in-gap stat
es are discussed. (C) 1999 Elsevier Science B.V. All rights reserved.