Localized magnetic moments in a Dirac semimetal as a spin model with long--range interactions

We connect between the problem of thermodynamics of localized magnetic moments in a Dirac semimetal, the interaction with relativistic electrons leading to the effective ferromagnetic exchange between the moments, and the existing theories dealing with long–range exchange interaction. We point out that the results of high–temperature expansion for the free energy of a dilute ensemble of magnetic impurities in the semimetal performed by V. Cheianov et al. (Phys. Rev. B {\bf 86}, 054424 (2012)) give an indication to the existence of a new disordered fixed point in such model.