Among the large number of promising two-dimensional (2D) atomic layer crystals, true metallic layers are rare. Through combined theoretical and experimental approaches, we report on the stability and successful exfoliation of atomically thin gallenene sheets, having two distinct atomic arrangements along crystallographic twin directions of the parent alpha-gallium. Utilizing the weak interface between solid and molten phases of gallium, a solid-melt interface exfoliation technique is developed to extract these layers. Phonon dispersion calculations show that gallenene can be stabilized with bulk gallium lattice parameters. The electronic band structure of gallenene shows a combination of partially filled Dirac cone and the non-linear dispersive band near Fermi level suggesting that gallenene should behave as a metallic layer. Furthermore it is observed that strong interaction of gallenene with other 2D semiconductors induces semiconducting to metallic phase transitions in the latter paving the way for using gallenene as interesting metallic contacts in 2D devices.
