  We present a deformed star-product for a particle in the presence of a
magnetic monopole. The product is obtained within a self-dual
quantization-dequantization scheme, with the correspondence between classical
observables and operators defined with the help of a quaternionic Hilbert
space, following work by Emch and Jadczyk. The resulting product is well
defined for a large class of complex functions and reproduces (at first order
in hbar) the Poisson structure of the particle in the monopole field. The
product is associative only for quantized monopole charges, thus incorporating
Dirac's quantization requirement.
