How to get the coordinates or .cif file of β  and χ ?
Jiang et al. 2018 (DOI: 10.1016/j.jechem.2018.01.026) may be relevant literature? Here's a quote:

These include three allotropes named borophene, beta-12(β12) and chi-3(χ3), which
have been successfully synthesized by physical methods [26,27].
[26] A. J. Mannix, X. F. Zhou, B. Kiraly, J. D. Wood, D. Alducin, B. D. Myers, X. L. Liu, B. L. Fisher, U. Santiago, J. R. Guest, M. J. Yacaman, A. Ponce, A. R. Oganv, M. C. Hersam, N. P. Guisinger, Science 350 (2015) 1513–1516.
[27] B. J. Feng. J. Zhang, Q. Zhong, W. B. Li, S. Li, H, Li, P. Cheng, S. Meng, L. Chen, K. H. Wu, Nat. Chem. 8 (2016) 563-568.

I also found this one:
Izadi Vishkayi, S., Bagheri Tagani, M. Edge-Dependent Electronic and Magnetic Characteristics of Freestanding β 12-Borophene Nanoribbons. Nano-Micro Lett. 10, 14 (2018). DOI: 10.1007/s40820-017-0167-z
Perhaps you may find the link to the .cif from all of the above?