F-spin symmetry in nuclei

A brief introduction is given to the concept of F-spin and mixed-symmetry in the framework of the interacting boson model (IBM-2) for heavy nuclei. Special attention is paid to mixed-symmetry multiphonon structures. The recent discovery of mixed-symmetry multiphonon structures in the nucleus 94Mo is presented. Experimental approaches and results are discussed. The most recent identification of similar structures in the N = 52 isotone 96Ru is addressed. (author)