Superconducting (SC) gap symmetry and magnetic response of cubic ${\mathrm{U}}_{0.97}{\mathrm{Th}}_{0.03}{\mathrm{Be}}_{13}$ are studied by means of high-precision heat-capacity and dc magnetization measurements using a single crystal, in order to address the long-standing question of its second phase transition at $T_{\mathrm{c}2}$ in the SC state below $T_{\mathrm{c}1}$. The absence (presence) of an anomaly at $T_{\mathrm{c}2}$ in the field-cooling (zero-field-cooling) magnetization indicates that this transition is between two different SC states. There is a qualitative difference in the field variation of the transition temperatures; $T_{\mathrm{c}2}\left(H\right)$ is isotropic, whereas $T_{\mathrm{c}1}\left(H\right)$ exhibits a weak anisotropy between the [001] and [111] directions. In the low-temperature phase below $T_{\mathrm{c}2}\left(H\right)$, the angle-resolved heat capacity $C(T,H,\varphi )$ reveals that the gap is fully opened over the Fermi surface, narrowing down the possible gap symmetry.

中文翻译：

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U0.97Th0.03Be13单晶中的准粒子激发和超导双跃迁的证据

超导（SC）间隙对称性和立方磁响应 ${\mathrm{ü}}_{0.97}{钍}_{0.03}{是}_{13}$ 通过使用单晶的高精度热容量和dc磁化测量来研究电势，以解决长期存在的第二相转变问题。 ${Ť}_{\mathrm{C}\mathrm{2个}}$ 在下面的SC状态 ${Ť}_{\mathrm{C}\mathrm{1个}}$。不存在（存在）异常${Ť}_{\mathrm{C}\mathrm{2个}}$在场冷却（零场冷却）中的磁化强度表明该转变是在两个不同的SC状态之间进行的。转变温度的场变化存在质的差异。${Ť}_{\mathrm{C}\mathrm{2个}}（H）$ 是各向同性的，而 ${Ť}_{\mathrm{C}\mathrm{1个}}（H）$在[001]和[111]方向之间表现出弱的各向异性。在下面的低温阶段${Ť}_{\mathrm{C}\mathrm{2个}}（H）$，角分辨热容量 $C（Ť，H，\varphi ）$ 揭示了该间隙在费米表面上完全打开，从而缩小了可能的间隙对称性。