  We present a model which can explain semiquantitatively a number of the
unusual properties of \mbox{Yb$_4$As$_3$}. The structural phase transition at
$T_{\text{c}}\simeq300\,\mbox{K}$ is described by a band Jahn-Teller effect of
correlated electrons and is interpreted as a charge ordering of the Yb ions.
The low carrier concentration in the low-temperature phase follows from the
strong electron correlations of the 4f-holes on the Yb sites and can be viewed
as self-doping of charge-ordered chains. The observed heavy-fermion behaviour
is on a scale of $T^\ast\simeq50\,\mbox{K}$ and is due to spinon-like
excitations in the Yb$^{3+}$-chains. The appearance of a second low-energy
scale around 0.2\,K is due to the Fermi energy of the low-density carriers.
