Let be a smooth projective curve and be a finite subgroup of Aut( ) 2 ⋊ ℤ 2 whose action is mixed, i.e. there are elements in exchanging the two isotrivial fibrations of × . Let 0 ⊲ be the index two subgroup ∩ Aut( ) 2 . If 0 acts freely, then ∶= ( × )∕ is smooth and we call it semi-isogenous mixed surface. In this paper we give an algorithm to determine semi-isogenous mixed surfaces with given geometric genus, irregularity and self-intersection of the canonical class. As an application we classify irregular semi-isogenous mixed surfaces with 2 > 0 and geometric genus equal to the irregularity; the regular case is subjected to some computational restrictions. In this way we construct new examples of surfaces of general type with = 1. We provide an example of a minimal surface of general type with 2 = 7 and = = 2.
K E Y W O R D SSurfaces of general type, finite group actions M S C ( 2 0 1 0 ) 14J29, 14L30, 14Q10