We describe an investigation of an unreactive interface, namely Sb on InP(110) clean cleaved surfaces. Transport techniques (I–V, C–V), Raman spectroscopy, and soft x-ray photoelectron spectroscopy have been used to study the Schottky barrier heights, overlayer structure, and interface interactions for Sb layers deposited on substrates held at room and low temperatures. The evolution of the overlayer structure at room temperature is complex, with an amorphous Sb layer growing on top of an ordered monolayer, until a thickness of ∼10 monolayers (ML), when the layer crystallizes. The evolution of the Schottky barrier is also complex but for thick layers we observe the lowest barriers on n-InP and the highest ever observed on p-InP. Possible mechanisms for the fact that the Fermi level appears pinned close to the conduction band are discussed.