Are there measurable quantities which directly depends on the Fermi velocity? The dispersion relation of electrons in, for example, graphene exhibits Dirac cones. The dispersion relation of a Dirac point at $\mathbf{k}=\mathbf{K}$ is linear in the momentum magnitude:
$$E=\pm v_F |{\bf k-K}|$$
where 
$v_F$ the Fermi velocity. 
The Fermi velocity can be measured directly by ARPES, or by any momentum-resolved spectroscopy. 
Are there measurable properties of the system which directly depends on the Fermi velocity in graphene, or in other systems where Dirac cones are present?
Addendum: To exemplify my question imagine that you could change in a gedanken experiment the velocity $v_F$ in the equation above, without changing the Fermi level or any other property of the system. Which physical quantities would be affected?
 A: To change $v_F$ is to change the dispersion and density of states, which you generally expect to have an affect on every electronic and optoelectronic property.
A particularly straightforward example: When you "gate" graphene (as you would a transistor), the fermi level moves, which you can measure most clearly by a cutting-off of IR absorption above a certain wavelength. The relation between gate voltage and IR absorption edge wavelength is given by a straightforward formula that involves $v_F$.
Gating also affects conductivity in a way related to $v_F$ for the same reason. (Actually conductivity and the IR absorption edge are related to each other by a "sum rule", ref.)
Apart from gate-based measurements: A high $v_F$ means that "the electrons move faster" which tends to increase electron mobility, other things equal. ...But mobility is also affected by defect scattering etc. So that's not an especially straightforward relationship.
If you could make a ballistic graphene electronic device (i.e., a device small enough and high-quality enough that there's no scattering), I bet $v_F$ would show up more directly in those measurements.
A: In a 2deg this is straightforward to measure from the temperature dependence of the shubnikov de haas oscillations, which depends directly on vf.
