  It is shown that a Dirac(-type) equation for a rank-two bi-spinor field on
Minkowski (configuration) spacetime furnishes a Lorentz-covariant
quantum-mechanical wave equation in position-space representation for a single
free photon. This equation does not encounter any of the roadblocks that have
obstructed previous attempts (by various authors) to formulate a
{quantum-mechanical} photon wave equation. In particular, it implies that the
photon wave function yields conserved non-negative Born-rule-type quantum
probabilities, and that its probability current density four-vector transforms
properly under Lorentz transformations. Moreover, the eigenvalues of the
pertinent photon Dirac Hamiltonian and the vector eigenvalues of the photon
momentum operator yield the familiar Einstein relations $E=\hbar\omega$ and
${\bf p}=\hbar{\bf k}$, respectively. Furthermore, these spin-1 wave modes are
automatically transversal without the need of an additional constraint on the
initial data. Some comments on other proposals to set up a photon wave equation
are supplied as well.
