Cold working of sodium metal converts body centred sodium metal to a mixture of a hexagonal form and body centred sodium at 5 K. The hexagonal from converts back to the body-centred form at 100-100 K.
Cold working of lithium metal converts body centred lithium metal to a mixture of a hexagonal form and body centred lithium at 78 K.
Potassium, rubidium, and caesium retain their body centred structure after cooling