Growth, thermal stability, and structure of ultrathin gallium films on Pd(111) and Pd(110) are investigated by low-energy ion scattering and low-energy electron diffraction. Common to both surface orientations are growth of disordered Ga films at coverages of a few monolayers (T = 150 K), onset of alloy formation at low temperatures (T ≈ 200 K), and formation of a metastable, mostly disordered ...