εdel4 R4 type invariants and their gradient expansion

We analyse the constraints from supersymmetry on. del(4) R-4 type corrections to the effective action in N = 2 supergravity in eight dimensions. We prove that there are two classes of invariants that descend respectively from type IIA and type IIB supergravity. We determine the first class as d-closed superforms in superspace in eight dimensions, whereas we obtain the second class by dimensional reduction down to four dimensions, in which there is a single class of invariants transforming in the next to minimal unitary representation of E-7(7).