I will review the recent construction of a large family of new supersymmetric AdS_5 solutions of M-theory, which were obtained using the method of G-structures. I will show how after dimensional reduction and T-duality, a countably infinite class of solutions are related to a new family of Sasaki-Einstein metrics on S^2 x S^3, which includes T^(1,1) and S^5 as special cases. These give rise to new solutions of type IIB supergravity which are expected to be dual to N=1 superconformal field theories in four dimensions with compact or non-compact R-symmetry and rational or irrational central charges, respectively. I will conclude with some comments on these SCFTs.

References : hep-th/0402153, hep-th/0403002