is modified as $n_{c}(x)=0.9+0.8x$ with $x$ being nominal doping.[@Erten2015] It is found in Ref.  that when $x>0.2$, the low-temperature London penetration depth shows a full gap behavior ($\Delta \lambda(T)\sim T^{n}$ with $n>2$). Therefore, such anomalous behavior of superfluid response strongly suggests that the superconducing pairing symmetry should change from nodal to nodeless structure. (See also Fig. \[fig:x1\].)

![\[fig:x1\] Change of pairing symmetry from nodal-d to nodeless-s wave at critical Yb-doping $x_{c}=0.2$ for Ce$_{1-x}$Co$_{x}$In$_{5}$.](x11.eps){width="0.9\columnwidth"}

Motivated by above observation, authors in Ref.  propose that the change of pairing symmetry may result from the formation of composite pairing, i.e. electrons in two orthogonal orbits screening the same local f-electron spin to form pairing. In this scenario, Yb-doping leads to a Lifshitz transition of nodal Fermi surface into a fully gapped composite-pairing molecular superfluid, thus the nodeless behavior observed in superfluid density measurement is expected.

Here we would like to propose an alternative possibility, i.e. the change of pairing structure may be just a doping effect but not related to emergence of exotic electron pairing. To be specific, we utilize our normal-state model in Sec. \[sec2\] and calculate the doping-dependence of the so-called pairing strength invented in Ref. , $$\begin{aligned}
\lambda^{\ast}\equiv\sum_{k\in FS}\gamma_{k}^{2}\nonumber.\end{aligned}$$ Here, the 