Magnetoresistance and Coupled Orbits in Tin

We have observed large quantum oscillations in the magnetoresistance of pure white tin at liquid-helium temperatures and in fields up to 150 kG. The oscillations are best developed when H is approximately 5^∘{} from the c axis and perpendicular to [110], and are interpreted as a magnetic breakdown effect which gives rise to a linear chain of coupled orbits. A calculation of the resistance, based on Pippard's suggestion that phase coherence is important only around small orbits, is in good agreement with the experimental results when fitted with a relaxation time for phase coherence of 2.3×{}10^-13 sec.