Cosmic structure formation in a flavoured U$\left(1\right)$ dark sector at small scales

In this work we study the footprint of a secluded dark sector with a U$\left(1\right)$ gauge symmetry on the formation of cosmic structure at small scales. A single generation of dark fermions with mass in the TeV range is able to elegantly solve all small-scale issues of structure formation, while still being consistent with the cosmological history of the universe. A new interaction at the MeV scale is introduced for this purpose. As a generalization we consider multiple generations of fermions as well and show that such extensions are also cosmologically viable and allow a more flexible choice of the parameters of the theory.