[NH3(CH2)3NH3]2[Ni(HP2O7)2(H2O)2] ⋅ 4H2O (NiDAP) is a new diphosphate of transition metallic and organic cations obtained from a mixture of H4P2O7, 2NiCO3⋅ Ni(OH)2 ⋅ 4H2O and NH2(CH2)3NH2 in a 1:1/6:1 molar ratio. This mixed organo-mineral compound crystallizes in the triclinic system, P¯, with the unit cell dimensions: a = 7.3678(3)~Å, b = 7.8018(5)Å, c = 11.1958(7)Å, α = 76.914(4), β = 81.052(4), γ = 85.46(1), V = 618.57(6)Å3 and Z = 1. The crystal structure of NiDAP consists of a complex anion, [Ni(HP2O7)2(H2O)2]4− and a diammoniumpropane cation. The complex anion is built up from two neutral water molecules (OW1) and two diphosphosphoric anions coordinated to Ni(II) in a bidentate chelating manner. (OW1) molecules link anionic complexes, [Ni(HP2O7)2(H2O)2]4− to create a thick bidimensional layers parallel to the (a, b) plane. These layers are interconnected in three dimensions through hydrogen bonds established between organic cations, the remaining water molecules OW2, OW3, and some external oxygen atoms of the anionic complex arrays. NiDAP was also characterized by IR spectroscopy, TG-DTA, and DSC analyses.