Distinction between critical current effects and intrinsic anomalies in the point-contact Andreev reflection spectra of unconventional superconductors

He Ge^{1, 2, †, ‡}, Wei Zhong-Xu^{1, 2, †}, Brisbois Jérémy^{3, †}, Jia Yan-Li^{1, 2}, Huang Yu-Long^{1, 2}, Zhou Hua-Xue^{1, 2}, Ni Shun-Li^{1, 2}, Silhanek Alejandro V³, Shan Lei^{1, 2, 4}, Zhu Bei-Yi¹, Yuan Jie¹, Dong Xiao-Li^{1, 2, 4}, Zhou Fang^{1, 2, 4}, Zhao Zhong-Xian^{1, 2, 4}, Jin Kui^{1, 2, 4}

(color online) Distinction between critical current effects and Andreev reflection. (a) PCAR spectra on an (Li_1−xFe_x)OHFeSe sample with T c = 38 K for temperatures between 5 K and 40 K. The inset shows the corresponding I(V) dependence at T = 5 K and the picture of surface taken by the scanning electron microscope. (b) Andreev reflection spectra obtained by calculations within the framework of the BTK model for temperatures between 0.5 T c and T_c. The inset shows the clear discrepancy between the experimental curve at T = 20 K (dots) and the result of fitting with the BTK model (red line).