We demonstrate that electron wave functions change their dimensionality at some commensurate directions of a magnetic field in conductors with open [quasi-one-dimensional (Q1D)] sheets of Fermi surface. These $1\mathrm{D}\to 2\mathrm{D}$ dimensional crossovers lead to delocalization of wave functions and are responsible for angular magnetoresistance oscillations. As an example, we show that suggested theory is in qualitative and quantitative agreement with the recent experimental data obtained on ${\left(\mathrm{TMTSF}\right)}_2{\mathrm{ClO}}_4$ conductor.

• Received 12 November 2004

DOI:https://doi.org/10.1103/PhysRevB.71.132504