2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/53766A large class of new 4-D superstring vacua with non-trivial/singular geometries, spacetime supersymmetry and other background fields (axion, dilaton) are found. Killing symmetries are generic and are associated with non-trivial dilaton and antisymmetric tensor fields. Duality symmetries preserving N=2 superconformal invariance are employed to generate a large class of explicit metrics for non-compact 4-D Calabi-Yau manifolds with Killing symmetries.LaTeX file, 13pp., CERN-TH.7121/93, HUB-IEP-93/8, LPTENS-93/51. (To appear in "Essays on Mirror Manifolds, II")High Energy Physics - Theorytext