(\mathrm{Ga}{3} \mathrm{P}{3} \mathrm{O}{12} \mathrm{~F}{2}, \mathrm{H}{3} \mathrm{~N}\left(\mathrm{CH}{2}\right){3} \mathrm{NH}{3}, \mathrm{H}{2} \mathrm{O}) was obtained by hydrothermal synthesis ( (453 \mathrm{~K}, 24 \mathrm{hr}), autogeneous pressure) from a mixture of (\mathrm{Ga}{2} \mathrm{O}{3}, \mathrm{P}{2} \mathrm{O}{5}, \mathrm{HF}, 1,3)-diaminopropane, and (\mathrm{H}{2} \mathrm{O}) in the ratio (1: 1: 2: 1.3: 80). It is orthorhombic (space group (P b c a) (No. 61) with (a=10.154(1) \AA, b=18.393(2) \AA, c=15.773(2) \AA, V=2945.8(9)) (\AA^{3}, Z=8). The three-dimensional network is built up from cornerlinked (\left[\mathrm{Ga}{3}\left(\mathrm{PO}{4}\right){3} \mathrm{~F}{2}\right]) units composed of three (\mathrm{PO}{4}) tetrahedra, two (\mathrm{GaO}{4} \mathrm{~F}) trigonal bipyramids, and one (\mathrm{GaO}{4} \mathrm{~F}{2}) octahedron. Fluorine atoms are shared between the octahedron and the bipyramid. The framework delimits 10 -membered ring channels along ([100]) and 8-membered ones along [101] and [10-1]. The amine and the water molecule are inserted in the 10 -membered ring channels. The hydrogen bonding scheme is discussed and shows that the water is principally linked to the amine within the tunnel and that the template might be the amine monohydrate. The thermal behavior of the title compound is studied by TGA and X-ray thermodiffractometry. O 1994 Academic Press, Inc.