We present a systematic study of the transport properties of n- and p-type Ge0.98Sn0.02 alloys using infrared spectroscopic ellipsometry and electrical measurements. We measure the dielectric function of our samples in the infrared range where the response is mainly due to free carrier absorption. In the case of p-type material, we observe, in addition to the free carrier response, optical transitions between split-off (SO), light (LH), and heavy-hole (HH) bands. The electron and hole mobilities for Ge 0.98Sn0.02 alloys with carrier concentrations >10 18cm-3 are comparable to those found in Ge samples with similar doping concentrations. The electron and hole effective masses of Ge 0.98Sn0.02 alloys are close to that of n-doped and p-doped Ge respectively.