The heterotic string and the geometry of the supersymmetric Einstein-Yang-Mills background

It is shown that the Wess-Zumino term of a heterotic superstring in aN = 1,D = 10 supergravity background can be given in terms of the torsion of the background in both versions (IA and IB) of theN = 1,D = 10 supergravity theory. The gauge degrees of freedom of the background are included according to the ideas of Kaluza and Klein. Explicit expressions for the vielbein, connection, torsion, and curvature of a space with 506 bosonic and 16 fermionic coordinates are given.