This was proposed as a metastable structure of gallium, visible for short times at atomospheric pressure. The true structure is isostructural with indium ($A6$), and stablized under pressure.
$\frac{3}{4}c \cos{\beta} \,\mathbf{\hat{x}}- b y_{1} \,\mathbf{\hat{y}}+\frac{3}{4}c \sin{\beta} \,\mathbf{\hat{z}}$
(4e)
Ga I
References
L. Bosio and A. Defrain, Structure cristalline du gallium β, Acta Crystallogr. Sect. B 25, 995 (1969), doi:10.1107/S0567740869003360.
Found in
J. Donohue, The Structures of the Elements (Robert E. Krieger Publishing Company, New York, 1974).
First cited in
D. Hicks, M.J. Mehl, M. Esters, C. Oses, O. Levy, G.L.W. Hart, C. Toher, and S. Curtarolo, The AFLOW Library of Crystallographic Prototypes: Part 3, Comp. Mat. Sci. 199, 110450 (2021). (doi=10.1016/j.commatsci.2021.110450)