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) The temperature dependence of FWHM of the NMR spectra, 1/T₁T, and the Knight shift K of (a)–(i) (Sr_1−xCa_x)₃Ir₄Sn₁₃ (x = 0, 0.5, 1) and (j)–(l) Ca₃RH₄Sn₁₃. The blue and red filled circles correspond to Sn(1) and Sn(2) sites, respectively. The purple dash lines indicate structural transition temperature T_s. The black dash dot lines indicate the temperature T* below which anomalies appear.