The invention provides nanocomposites comprising a clay and an organic compound, in which the clay is a clay bridged by a metal compound, preferably iron oxide and/or aluminum oxide. The organic compound is preferably a polymer. The clay-based nanocomposites of the invention have good mechanical properties and good heat resistance. The invention also provides cables comprising such a nanocomposite, preferably in their sheath or outer coating. Finally, the invention provides a process for producing said nanocomposite.