The strongly correlated actinide metal URu₂Si₂ exhibits a mean field-like second order phase transition at T_o ≈ 17 K, yet lacks definitive signatures of a broken symmetry. Meanwhile, various experiments have also shown the electronic energy gap to closely resemble that resulting from hybridization between conduction electron and 5f-electron states. We argue here, using thermodynamic measurements, that the above seemingly incompatible observations can be jointly understood by way of proximity to an entropy-driven critical point, in which the latent heat of a valence-type electronic instability is quenched by thermal excitations across a gap, driving the transition second order. Salient features of such a transition include a robust gap spanning highly degenerate features in the electronic density of states, that is weakly (if at all) suppressed by temperature on approaching T_o, and an elliptical phase boundary in magnetic field and temperature that is Pauli paramagnetically limited at its critical magnetic field.

的强烈的相关性锕系金属URU ₂的Si _2所显示的平均场状的第二阶相的转变Ť _ö  ≈17 K，但缺乏破对称的明确的签名。同时，各种实验还表明，电子能隙与传导电子和5 f的杂化所产生的电子能隙非常相似。-电子态。我们在这里使用热力学测量方法论证，可以通过接近熵驱动的临界点来共同理解上述看似不相容的观察结果，其中价型电子不稳定性的潜热通过跨间隙的热激发来淬灭，驱动过渡二阶。这种转变的显着特征包括一个健壮的间隙，该间隙跨越状态的电子密度中的高度简并特征，在达到T _o时温度会弱抑制（如果有的话），并且磁场和温度中的椭圆相边界为Pauli在其临界磁场下顺磁性地受到限制。