Hsieh, L. Fu, and P. Gegenwart for discussions on Luttinger model and Gruneisen number. This work was supported by NSF Grant DMR-1151208 and Hellman Family Foundation (EGM, CX), the David and Lucile Packard Foundation, the Alfred P. Sloan Foundation (CX), NSF–DMR–1206809 (LB), and NSERC, CIFAR (YBK). YBK and LB acknowledge the support and hospitality from the Aspen Center for Physics, funded by NSF grant PHY-1066293, and the KITP, funded by NSF grant PHY–1125915.

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