This paper answers two questions: how to stabilize an exclusively pentagonal composed silicon allotrope? Is it possible to realize ferroelectricity in 2D elemental material, using Si, which is the basis of today's semiconductor technology?

See: Lattice Dynamic and Instability in Pentasilicene: A Light Single-Element Ferroelectric Material With High Curie Temperature. Phys. Rev. Appl. 11, 064063 (2019).