  We give a complete list of the points in the spectrum
$$\mathcal{Z}=\{\inf_{(x,y)\in\Lambda,xy\neq0}{\left\vert
xy\right\vert},\,\text{$\Lambda$ is a unimodular rational lattice of
$\mathbb{R}^2$}\}$$ above $\frac{1}{3}.$ We further show that the set of limit
points of $\mathcal{Z}$ with values larger than $\frac{1}{3},$ is equal to the
set $\{\frac{2m}{\sqrt{9m^2-4}+3m},\text{ where $m$ is a Markoff number}\}$.
