Abstract: A semiconducting, cross-linkable and silane-containing polymer composition is disclosed, as is a cable sheathing for an electric cable which, as semiconducting layer, includes the cross-linked polymer composition. The composition is based on ethylene and contains carbon black. Preferably, the polymer is a terpolymer of ethylene, a (meth)acrylate of an alcohol having 1-8 carbon atoms, such as methyl, ethyl or butyl acrylate, and an unsaturated silane compound, such as vinyltrimethoxy silane. The polymer composition is distinguished by the fact that the carbon black has a specific surface area of approximately 30-80 m.sup.2 /g, which reduces the problems associated with undesirable cross-linking of the polymer composition, for instance in extrusion.