  We have synthesized new Tsai-type Yb-based intermediate-valence approximant
crystals (ACs) with different degree of approximation to quasicrystal,
Zn--Au--Yb 1/1 and 2/1 AC, and studied the external pressure effect on their Yb
mean-valence $\nu$. Whereas 1/1 AC distinctly exhibits a first-order-like jump
in $\nu$ at a transition pressure $P_{\rm v}$, 2/1 AC only shows an indistinct
anomaly at $P_{\rm v}$. We have also studied the pressure dependence of the
$\nu$ of Au--Al--Yb 1/1 AC, which is a prototypal AC exhibiting
pressure-induced quantum criticality. It shows a continuous valence anomaly at
a critical pressure $P_{\rm c}$ where the magnetic susceptibility diverges
toward zero temperature, in contrast to the valence jump in the Zn--Au--Yb 1/1
AC. These results are discussed based on a theoretical model of quantum
critical valence fluctuation.
