  A wide array of unusual phenomena has recently been uncovered in kagome
solids. The charge density wave (CDW) state in the kagome superconductor AV3Sb5
in particular intrigued the community -- the CDW phase appears to break the
time-reversal symmetry despite the absence of spin magnetism, which has been
tied to exotic orbital loop currents possibly intertwined with magnetic field
tunable crystal distortions. To test this connection, precise determination of
the lattice response to applied magnetic field is crucial, but can be
challenging at the atomic-scale. We establish a new scanning tunneling
microscopy based method to study the evolution of the AV3Sb5 atomic structure
as a function of magnetic field. The method substantially reduces the errors of
typical STM measurements, which are at the order of 1% when measuring an
in-plane lattice constant change. We find that the out-of-plane lattice
constant of AV3Sb5 remains unchanged (within 10^-6) by the application of both
in-plane and out-of-plane magnetic fields. We also reveal that the in-plane
lattice response to magnetic field is at most at the order of 0.05%. Our
experiments provide further constraints on time-reversal symmetry breaking in
kagome metals, and establish a new tool for higher-resolution extraction of the
field-lattice coupling at the nanoscale applicable to other quantum materials.
