Infrared Reflectance and Optical Conductivity of GdAlSi Single Crystal

Altermagnets are a newly identified class of magnetic materials that break time-reversal symmetry while maintaining zero net magnetization. This unique property results in symmetry-protected, momentum-dependent spin splitting without conventional ferromagnetic characteristics. In this work, we study GdAlSi single crystal, an altermagnet candidate that also exhibits a magnetic Weyl semimetal property. We measured the infrared reflectance of the GdAlSi single crystal over a broad frequency range. Using Kramers-Kronig analysis, we extracted the complex optical conductivity and compared the results with dc transport measurements to evaluate consistency and identify charge carrier dynamics. Prior to the measurement, the crystal surface was polished, and the crystallographic axes were identified. To probe potential anisotropies in optical conductivity associated with the crystal symmetry, we performed polarization-dependent reflectance measurements. The measured spectral features provide new insight into characterizing GdAlSi electronic property as an altermagnet and Weyl semimetal.