Abstract

At ordinary conditions, almost all the metallic elements adopt simple, densely-packed crystal structures. Until 15 years ago, the same was assumed to apply generally at high pressure, but this expectation has proved to be spectacularly wrong. Numerous elements across the periodic table are now known to adopt very complex crystal structures at high pressure, with profound effects on their physical properties. The archetypal simple metals lithium and sodium have been reported to become semiconductors; many of the complex phases are superconducting at low temperature, and potassium has been predicted to become magnetic under pressure. An overview of the research that has led to a dramatic change of our understanding of the structural and physical properties of elemental metals at high pressure will be given. I will then discuss and illustrate how these advances can benefit the research on thermoelectric materials, where structural complexity is a sought-after property.