Guanjun Xiao, Ye Cao, Guangyu Qi, Lingrui Wang, Qingxin Zeng, Chuang Liu, Zhiwei Ma, Kai Wang, Xinyi Yang, Yongming Sui, Weitao Zheng,* and Bo Zou*, “Compressed few-layer black phosphorus nanosheets from semiconducting to metallic transition with the highest symmetry”