NOVELTY - Use of first and second polymeric materials for producing at least one first layer (1.1) and at least one additional layer (1.2) of a multilayer tube (1) or a multilayer tube molding for a tube assembly of a geothermal energy production or storage device, is claimed.    USE - The first and second polymeric materials are useful for producing a layer of a multilayer tube or a multilayer tube molding for a tube assembly of a geothermal energy production or storage device (claimed).    ADVANTAGE - The first and second polymeric materials provide resistant against damages, crack and high temperatures arising form air conditioning and long life to the tube and tube molding, and can be easily processed.    DETAILED DESCRIPTION - Use of first and second polymeric materials for producing at least one layer (1.1) and at least one additional layer (1.2) of a multilayer tube or a multilayer tube molding for a tube assembly of a geothermal energy production or storage device, is claimed. The first polymeric material is a non-crosslinked polyolefin, and has a resistance to internal pressure, which is at or above a reference curve in the temperature of 10-110 degrees C, measured according to ISO 9080, and corresponds to an equation as given in the specification. The second polymeric material is a non-crosslinked polyolefin, and has a minimum required strength value of greater than 10 MPa and a full notched creep test (FNCT) value in accordance with ISO 16770 at 80 degrees C and sigma 4 N/mm2 at 1% of Arkopal (RTM: Nonionic surfactant) of greater than 10000 hours. INDEPENDENT CLAIMS are included for:    (1) the multilayer tube or a multilayer tube molding, comprising a connecting element, a pipe bend, a pipe branch, a T-piece, a sleeve or electric welding sleeve, obtained using the first and the second polymeric material;    (2) the tube assembly having at least one multilayer tube and the multilayer tube molding; and    (3) the geothermal production or storage device comprising the tube assembly.    DESCRIPTION OF DRAWING(S) - The figure shows a cross sectional side view of a multilayer tube.    Multilayer tube (1)    First layer (1.1)    Additional layer (1.2)    Lumen (2)    Outer layer. (3)