Sheet packaging material for producing sealed packages for pourable food products, sealed package for pourable food products and a method of manufacturing a sealed package for pourable products

A pre-creased sheet packaging material for forming a sealed package, comprising:

• a plurality of longitudinal crease lines, which extend along a longitudinal first direction of said sheet packaging material;
• a plurality of transversal crease lines, which extend along a transversal second direction of said sheet packaging material, which is transversal to said first longitudinal direction;
• at least one first additional crease line, which extends along a third direction, which is slanted with respect to said first longitudinal direction and said second transversal direction;
• a first joining point, at which a first said longitudinal crease line and a first said transversal crease line join with respect to one another;
• and
• at least one first area, which is bounded by at least one portion of said first longitudinal crease line, said first transversal crease line and said first additional crease line;
• said first area being configured to form a first folded flap of said formed package;
• said third direction being incident to said first longitudinal crease line and to said first transversal crease line in said first joining point;
• and
• at least one of said first longitudinal crease line, at least one first transversal crease line and said first additional crease line beinq interrupted at said first joining point.