  Polar metals based on binary and ternary compounds have been demonstrated in
literature. Here, we propose a design principle for ferroelectric-like
elemental polar metals and relate it to real materials. The design principle is
that, to be an elemental polar metal, atoms should occupy at least two
inequivalent Wyckoff positions in a crystal with a polar space group, where
inversion symmetry is spontaneously broken. According to this rule, we propose
the first class of potential ferroelectric-like elemental polar metals in a
distorted {\alpha}-La-like structure with a polar space group P63mc in which
two inequivalent Wyckoff positions 2a (0, 0, z) and 2b (1/3, 2/3, z) are
occupied by group-V elements (phosphorus, arsenic, antimony, and bismuth).
Analyses based on first-principles calculations indicate that the dynamically
stable polar phase results from a lone pair driven polar distortion of the
nonploar phase in P63/mmc symmetry where two inequivalent Wyckoff positions 2a
(0, 0, 0) and 2c (1/3, 2/3, 1/4) are occupied. This ferroelectric-like
transition involves a transition from a metallic state to a semimetallic state.
These predicted polar phases are metastable with respect to their corresponding
ground phases. Moreover, ionic bonding characters are found due to the
inequivalence in Wyckoff positions between group-V atoms. Our work opens a
route to single-element parity-breaking phases.
