Investigations of the last decade significantly extended the list of known zeolite-like compounds, whose crystal structure is based on mixed frameworks composed of various anion polyhedra. In addition to the well-known natural and artificial zeolites with the Al and Si tetrahedron frameworks, a large number of microporous phases with three-dimensional anion constructions based on Zn‐P, Be‐P, Zn‐As, Al‐P, and other cation matrices were found [1‐6]. Oxygen complexes of amphoteric metals in combination with [ PO 4 ] 3— acid complex anions form mixed anion frameworks containing pores or channels, where either alkaline or organic cations are located. In this group of compounds, which are often used as molecular sieves as an alternative to aluminum silicates, aluminum phosphates are most studied. Systematically investigating aluminum phosphates, we synthesized one more such compound. In this work, we study colorless transparent isometric well-cut crystals up to 5 mm in size, which were produced in standard Teflon-lined 4-cm 3 autoclaves by the method of soft hydrothermal synthesis ( T = 250i C and P = 100 atm). A mechanical mixture of Na 2 O‐ Al 2 O 3 ‐P 2 O 5 ‐B 2 O 3 components prepared in equal weight amounts was introduced into a water-filled autoclave. Experiments continued for 18‐20 days. The diffraction pattern recorded from a powder sample by a DRON UM diffractometer indicated that the synthesized compound is original. The X-ray analysis (CanScan 4DV) showed that this phase include Na, Al, and P atoms. Investigating a single crystal with a SYNTEX P four-circle autodiffractometer, we found that the parameters of a rhombic (pseudotetragonal) unit cell are a = 8.475(2) A , b = 8.471(2) A, and c = 14.319(3) A. Experimental data needed to interpret the structure were obtained with the same diffractometer (Mo K α radia1 tion) by the 2 θ : θ -scanning method. The intensities of reflexes were adjusted with allowance for the Lorenz factor and polarization effect. Calculations were made with the SHELX program package [7, 8] by using the curves of atomic scattering and the corrections for anomalous dispersion taken from [9]. We could not find a structural model in the framework of the tetragonal symmetry ( P 4 2 2 1 2 space group). For this reason, we supposed that the crystal has rhombic symmetry, and the pseudotetragonal symmetry results from merohedric or pseudomerohedric microtwinning. The structure was determined by direct methods and refined in the anisotropic full-matrix approximation with allowance for absorption and secondary isotropic extinction. In the absence of chemical analysis, atoms were identified by taking into account the composition of the system in the process of crystal synthesis, interatomic spacings, temperature factors, and the character of ellipsoids of thermal vibrations. Allowance for pseudotetragonal twinning showed that the samples under investigation contain two kinds of objects with different orientations in a ratio of 0.440(3) : 0.560(3). The Flack parameter [10] testified to the proper choice of an “absolute” acentric configuration ( P 2 1 2 1 2 1 space group). The structure is described by the formula