  We report the results of the first directional point-contact measurements in
Mg(B_{1-x}C_{x})_2 single crystals with 0.047 <= x <= 0.132. The two-gap
superconductivity typical of MgB_2 persists up to x=0.105. In this region, the
values of the gaps Delta_{sigma} and Delta_{pi} were determined by fitting the
Andreev-reflection conductance curves with a two-band Blonder-Tinkham-Klapwijk
(BTK) model, and confirmed by the single-band BTK fit of the sigma- and pi-band
conductances, separated by means of a magnetic field. At x=0.132, when T_{c}=19
K, we clearly observed for the first time the merging of the two gaps into one
of amplitude Delta~3 meV.
