Fig. 10.

Superconducting upper critical field. The superconducting upper critical fields $H_{c2}$ of the QC, the 2/1AC, the 1/1AC_F are plotted in the form of $h=-H_{\mathrm{c}2}∕\left(T_{\mathrm{c}}\mathrm{d}{H}_{\mathrm{c}2}∕\mathrm{d}T{\mid }_{T=T_{\mathrm{c}}}\right)$ vs $t=T∕T_{\mathrm{c}}$. The solid curve denotes the Werthamer–Helfand–Hohenberg theory in the dirty limit. The inset shows $H_{\mathrm{c}2}\left(T\right)$ of the same samples as in the main frame. Note that the upper critical field in the limit of zero temperature of the 1/1AC_F ($H_{c2}\left(0\right)\cong 500$ Oe) substantially exceeds that of metal Al ($~100$ Oe), excluding the possibility that the superconductivity would arise from Al-derived impurity phase