  Lanthanum (La), the first member of the rare-earth elements, recently aroused
strong interest due to its unique superhydride with superconducting properties.
Although there is much theoretical and experimental work about phase
transitions and superconductivity in metallic La, we got a new body-centred
tetragonal ($bct$) phase in metallic La with space group $I4/mmm$ at $190$ GPa
exchanging from face-centered cubic ($fcc$) phase in previous work, which
expanded the phase transition sequence. The $bct$ phase shows an abnormal
packing way that turned to non-closed packing at high pressure. And more
detailed properties of the new phase are discussed.
