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Elastic properties of hidden order in URu$_{\text2}$Si$_{\text2}$ are reproduced by a staggered nematic

We develop a phenomenological mean field theory describing the hidden order phase in URu$_{\text2}$Si$_{\text2}$ as a nematic of the $\text B_{\text{1g}}$ representation staggered along the $c$-axis. Several experimental features are reproduced by this theory: the topology of the temperature--pressure phase diagram, the response of the elastic modulus $(C_{11}-C_{12})/2$ above the transition at ambient pressure, and orthorhombic symmetry breaking in the high-pressure antiferromagnetic phase. In this scenario, hidden order is characterized by broken rotational symmetry that is modulated along the $c$-axis, the primary order of the high-pressure phase is an unmodulated nematic, and the triple point joining those two phases with the high-temperature paramagnetic phase is a Lifshitz point.