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].
 A. J. Mannix, X. F. Zhou, B. Kiraly, J. D. Wood, D. Alducin, B. D. Myers, X. L. Liu, B. L. Fisher, U. Santiago,...