Inducing Complexity in Intermetallics through Electron-Hole Matching: The Structure of Fe₁₄ Pd₁₇ Al₆₉

We illustrate how the crystal structure of Fe₁₄ Pd₁₇ Al₆₉ provides an example of an electron-hole matching approach to inducing frustration in intermetallic systems. Its structure contains a framework based on IrAl_2.75 , a binary compound that closely adheres to the 18-n rule. Upon substituting the Ir with a mixture of Fe and Pd, a competition arises between maintaining the overall ideal electron concentration and accommodating the different structural preferences of the two elements. A 2×2×2 supercell results, with Pd- and Fe-rich regions emerging. Just as in the original IrAl_2.75 phase, the electronic structure of Fe₁₄ Pd₁₇ Al₆₉ exhibits a pseudogap at the Fermi energy arising from an 18-n bonding scheme. The electron-hole matching approach's ability to combine structural complexity with electronic pseudogaps offers an avenue to new phonon glass-electron crystal materials.