Effect of 3$p$- and 5$d$-electron doping on the Kondo Semiconductor CeFe$2$Al${10}$

We examined the effect of $3p$- and $5d$-electron doping on the Kondo semiconductor CeFe$_2$Al$_{10}$ by means of the electrical resistivity ($\rho$), magnetic susceptibility ($\chi$), and specific heat ($C$) measurements. The results show that in the $3p$-electron-doped system CeFe$_2$Al$_{10-y}$Si$_y$, the semiconducting behavior is suppressed for $y = 0.05$, and the system adopts a metallic ground state with an increase in the density of states at the Fermi level. The Si substitution leads to a large decrease in the paramagnetic Weiss temperature $\theta_P$ indicating a reduction in $c \mbox{-} f$ hybridization strength, however, the Si does not induce magnetic order up to $y = 0.3$ down to 2~K. The systematic changes in $\rho$($T$), $\chi$($T$), and $C$($T$) are similar to those for $5d$-electron doped system CeFe$_{2-x}$Ir$_{x}$Al$_{10}$, although, Ir substitution induces a bulk antiferromagnetic transition below 3.1~K in CeFe$_{1.7}$Ir$_{0.3}$Al$_{10}$. These changes can be explained by the collapse of the hybridization gap due to the suppression of the $c\mbox{-}f$ hybridization effect. Our results further confirm that the collapse of the spin/charge gap by an excess electron doping is one of the universal features of the Kondo semiconductors Ce$T_2$Al$_{10}$ ($T$ = Fe, Ru, and Os)