Superconductivity in noncentrosymmetric ${\mathrm{LaNiC}}_2$ is expected to be induced by electron-phonon interactions due to its lack of magnetic instabilities. The non-Bardeen-Cooper-Schrieffer (BCS) behaviors found in this material call into question the long-standing idea that relates unconventional superconductivity with magnetic interactions. Here we report magnetic penetration-depth measurements in a high-purity single crystal of ${\mathrm{LaNiC}}_2$ at pressures up to 2.5 GPa and temperatures down to 0.04 K. At ambient pressure and below $0.5T_c$ the penetration depth goes as $T^4$ for the in-plane and $T^2$ for the out-of-plane component, firmly implying the existence of point nodes in the energy gap and the unconventional character of this superconductor. The present study also provides evidence of magnetism in ${\mathrm{LaNiC}}_2$ by unraveling a pressure-induced antiferromagnetic phase inside the superconducting state at temperatures below 0.5 K, with a quantum critical point around ambient pressure. The results presented here maintain a solid base for the notion that unconventional superconductivity only arises near magnetic order or fluctuations.

中文翻译：

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LaNiC2单晶中的非常规超导性和环境压力磁量子临界点

非中心对称的超导 ${\mathrm{镍镉合金}}_{\mathrm{2个}}$由于缺乏磁性的不稳定性，预计它是由电子-声子相互作用引起的。在该材料中发现的非巴登-库珀-施里弗（BCS）行为使人们质疑将非常规超导性与磁相互作用相关联的长期观念。在这里，我们报告了高纯度单晶硅中的磁渗透深度测量${\mathrm{镍镉合金}}_{\mathrm{2个}}$ 在最高2.5 GPa的压力和最低0.04 K的温度下。在环境压力及以下 $0.5{Ť}_C$ 穿透深度为 ${Ť}^4$ 用于面内和 ${Ť}^{\mathrm{2个}}$对于平面外组件，坚决暗示在能隙中存在点节点，并且暗示了该超导体的非常规特性。本研究还提供了磁性的证据。${\mathrm{镍镉合金}}_{\mathrm{2个}}$通过在低于0.5 K的温度下解开超导态内部的压力感应反铁磁相，并在环境压力附近建立一个量子临界点。此处给出的结果为非常规超导仅在磁阶或波动附近产生的观点奠定了坚实的基础。