A new representative of the RAuIn series was discovered in the Sc-Au-In system. ScAuIn crystallizes in the hexagonal HfRhSn-type structure (space group P-62c) with a ​= ​0.75667(2), c ​= ​0.71873(2) nm). Magnetization measurements revealed that ScAuIn is a Pauli paramagnet with magnetic susceptibility of ∼6 ​× ​10⁻⁵ emu/mol. The Sommerfeld coefficient γ of 2.8 ​mJ ​K⁻² ​mol⁻¹ derived from the specific heat measurements is comparable with those obtained from the modeled density of states at the Fermi level N(E_F). Ab initio calculations predict metallic conductivity and show strong chemical bonding within the [InAu] sublattice. The structural stability of the RAuIn with ZrNiAl and HfRhSn structure types is discussed based on crystal chemistry analysis and DFT modeling.