Prepd by thermal decompn of ammonium hexafluogallate (NH4)3(GaF6): Hannebohn, Klemm, Z. Anorg. Allg. Chem. 229, 342 (1936); Kwasnik in Handbook of Preparative Inorganic Chemistry vol. 1, G. Brauer, Ed. (Academic Press, New York, 2nd ed., 1963) pp 227-228; from Ga and HF: Brewer et al., J. Inorg. Nucl. Chem. 9, 56 (1959); Muetterties, Castle, ibid. 18, 148 (1961).