New representatives of the A₂M₃(SO₄)₄ (A = Rb and Cs, M = Co, Ni) family were found, inspired by the discovery and characterization of itelmenite, a mineral of composition Na₂CuMg₂(SO₄)₄. Four new compounds were obtained by high-temperature solid-state reactions in air. All new compounds were structurally characterized by single-crystal and powder X-ray diffraction. Rb₂Ni₃(SO₄)₄ and Rb₂Co₃(SO₄)₄ crystallize in the monoclinic space group P2₁/c, Cs₂Ni₃(SO₄)₄ in P2₁/n whereas Rb₂Co₃(SO₄)₄ crystallizes in the orthorhombic space group P2₁2₁2₁. In order to determine the temperature of crystallization of the new phases DTA and TG were performed for the mixtures of the precursors. Several synthesis strategies were tested and discussed. The investigation of the reactivity upon heating highlights the stability of the precursors before they collapse, explaining the difficulties to get pure powder samples.