An improved method of beam deposition to deposit a low-resistivity metal. Preferred embodiments of the present invention use a novel focused ion beam induced deposition precursor to deposit low-resistivity metallic material such as tin. Applicants have discovered that by using a methylated or ethylated metal such as hexamethylditin as a precursor, material can be deposited having a resistivity as low as 40 μΩ·cm.