Gram quantities of a new adduct based on light fullerene tris-malonate samarium salt С₆₀ [C₆₀(=C(COO)₂)₃]Sm₂ are obtained via the reaction of ion exchange. The obtained adduct is studied by means of electron and infrared spectroscopy, X-ray and elemental analysis, electron microscopy, and thermogravimetry. The polythermal solubility of [C₆₀(=C(COO)₂)₃]Sm₂ in water is determined in ampoules via saturation within 20–70°C. The composition of crystalline hydrate [C₆₀(=C(COO)₂)₃]Sm₂ · 36Н₂О, which exists in equilibrium with the saturated solution, is estimated.