Scientific Achievement Two stage nematic bond ordering above double stripe magnetism in BaTi2Sb2O Scientific Achievement Introduced and explored the concept of  a multiple stage spin-driven nematicity, whereby a magnetic order that breaks n lattice symmetries can undergo up to n+1 distinct phase transitions. Significance and Impact Thus far, spin-driven nematicity has been restricted to the case of single-stripe magnetism. Here we show this phenomena is much broader, both conceptually and in terms of applications; this research should have important implications for superconductivity. Research Details We developed a low-energy field theory of the nematic transitions above double-stripe magnetism, and showed that it can have, as a function of temperature, up to two separate bond-order phase transitions -- one that breaks rotation and one that breaks reflection and translation of the lattice. Used first principles calculations to find a material (BaTi2Sb2O) that satisfies the conditions for this new two- stage nematic mechanism, and showed consistency with experimental observations. figure Single stripe magnetism Double stripe magnetism 185 word summary Temperature Control parameter G. Zhang, J. K. Glasbrenner, R. Flint, I. I. Mazin, R.M. Fernandes, PRB 95, 174402 (2017) G. Zhang, R. Flint, arXiV:1708.04189 (under review at PRB)