A multilayer sheet of packaging material for producing a sealed a package

A multilayer sheet of packaging material for producing a sealed package of a pourable food product, said packaging material comprising:

• at least one base layer for imparting stiffness;
• a plurality of lamination layers applied to and covering both sides of said base layer;
• a pre-laminated opening which is formed by a through slot provided in said base layer and covered by one or more of said lamination layers, said pre-laminated opening being configured to receive an opening device for outpouring the pourable food product;
• a plurality of folding lines configured to define an edge between two adjacent walls of a sealed package formed by folding and sealing the packaging material, wherein the pre-laminated opening is not intersected by any one of said folding lines,
• the pre-laminated opening including an outer rim extending between a first end and a second end distanced from the first end, wherein the outer rim is arc-shaped so as to define a first portion of a first circumference.