We present two-parameter solutions of the low-energy four-dimensional
heterotic string which in the extremal limit reduce to supersymmetric monopole,
string and domain wall solutions. The effective scalar coupling to the Maxwell
field, e−αϕFμνFμν, gives rise to a new string
black hole with α=3, in contrast to the pure dilaton black hole
solution which has α=1. Implications of string/fivebrane duality in
D=10 to four-dimensional dualities are discussed.Comment: Based on talks given at MRST 94, McGill University and at
Mini-workshop on Extended Objects, Newton Institute, March 1994, 4 pages, Te