Abelian hypercomplex 8-dimensional nilmanifolds

We study invariant Abelian hypercomplex structures on 8-dimensional nilpotent Lie groups. We prove that a group N admitting such a structure is either Abelian or an Abelian extension of a group of type H. We determine the Poincare polynomials of the associated nilmanifolds and study the existence of symplectic and quaternionic structures on such spaces.