A multi-layer sheet suitable as sealable or peelable sheet specially used for closing foodstuff containers. This multi-layer sheet comprises a polymeric substrate layer and a seal or a peel-seal layer. The multilayer composite film has at least two main component layers, namely in order, a polymeric substrate layer for mechanical strength and a heat-sealable layer applied by extrusion-coating, comprising a polyester of at least one aromatic dicarboxylic acid and at least one aliphatic dicarboxylic acid and at least one aliphatic diol. The polyester substrate layer comprises a crystallizable polyester base layer and an amorphous polyester sealable skin layer. The heat-sealable layer is slow-crystallizing with a glass transition temperature 50° F. or lower and melting point 250-320° F.