Structural phase transition, precursory electronic anomaly, and strong-coupling superconductivity in quasi-skutterudite (Sr1−<italic>x</italic>Ca<italic>x</italic>)3Ir4Sn13 and Ca3Rh4Sn13<xref rid="cpb_27_7_077401fn1" ref-type="fn">*</xref><fn id="cpb_27_7_077401fn1"> <label>*</label>Project supported by the National Natural Science Foundation of China (Grant Nos. 11674377 and 11634015), the National Key R&D Program of China (Grant Nos. 2017YFA0302904 and 2016YFA0300502), and the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (Grant No. XDB07020200). J. Y. is supported by the Youth Innovation Promotion Association of CAS.</fn>

Structural phase transition, precursory electronic anomaly, and strong-coupling superconductivity in quasi-skutterudite (Sr_1−xCa_x)₃Ir₄Sn₁₃ and Ca₃Rh₄Sn₁₃* *

Project supported by the National Natural Science Foundation of China (Grant Nos. 11674377 and 11634015), the National Key R&D Program of China (Grant Nos. 2017YFA0302904 and 2016YFA0300502), and the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (Grant No. XDB07020200). J. Y. is supported by the Youth Innovation Promotion Association of CAS.

Luo Jun^{1, 2}, Yang Jie^{1, †}, Maeda S³, Li Zheng^{1, 2}, Zheng Guo-Qing^{1, 2, 3, ‡}

(color online) (a) The temperature dependence of the Knight shift for Ca₃Ir₄Sn₁₃ at H₀ = 0.4 T. The arrow indicates T_c. (b) The temperature dependence of 1/T₁ below 10 K. (c) The temperature dependence of 1/T₁ below T_c in semilogarithmic coordinate. The solid line represents the relation 1/T₁ ∝ exp(−Δ/k_BT).