neutrality point, electrons in graphene obey the Dirac equation $\varepsilon\Psi=H\Psi$. In principle two species of Dirac fermion should be distinguished because the low-energy spectrum of graphene consists of two sets of Dirac cones. However, since the fields $\bm A$ and $U$ are smooth, no scattering between species is possible. Furthermore, by employing here the valley-isotropic representation,[@Been07] the Hamiltonians for the two valleys are rendered identical, not only in form, but also in the actual values assumed by the parameters. An index that distinguishes between valleys is therefore omitted. Results obtained will apply equally to electrons in both valleys unless otherwise indicated.

I consider a magnetic field $B\hat{\bm{z}}=\bm{\partial}_{\bm{r}}\times\bm{A}$ and a scalar potential $U$ that are periodic in space with the same periodicity and that average to zero. The periodicity of the fields define a Bravais lattice with a primitive unit cell denoted $UC$ and basis vectors $\bm{a}_k$, $k=1,\,2$, such that $B(\bm{r}+\bm{a}_k)=B(\bm{r})$ and similarly for $U$.

In what follows, any function that has this property will be called $UC$-periodic. Furthermore, whenever the term ‘lattice’ is used below, it will refer to the magnetic field lattice, not the crystal lattice of the carbon atoms in graphene. The two lattices are entirely distinct and 