Control of electronic properties of (formula presented) (formula presented) by the uniaxial strain method

Systematic uniaxial strain studies of (formula presented) (formula presented) have been carried out. By controlling the in-plane lattice parameters a and c independently, we find that both compounds have essentially the same phase diagram in electronic properties, although, under the hydrostatic pressures, they show quite different phase diagrams. The K salt shows the superconductivity like (formula presented) salt under the c-axis uniaxial strain, and the latter undergoes a transition to the density-wave state like the former under the a-axis uniaxial strain. These changes in electronic structures are verified by measuring the angle-dependent magnetoresistance. The electronic properties of these compounds can be systematically understood as a function of (formula presented) the ratio of the in-plane lattice parameters.