  The existence of maximally supersymmetric solutions to heterotic string
theory that are not toroidal compactifications of the ten-dimensional
superstring is established. We construct an exact fermionic realization of an
N=1 supersymmetric string theory in D=8 with non-simply-laced gauge group
Sp(20). Toroidal compactification to six and four dimensions gives maximally
extended supersymmetric theories with reduced rank (4,12) and (6,14)
respectively.
