Point-contact spectroscopy on antiferromagnetic Kondo semiconductors CeT₂Al₁₀ (T=Ru and Os)

We have carried out point-contact spectroscopy (PCS) measurements on one family of antiferromagnetic Kondo semiconductor CeT₂Al₁₀ (T=Ru and Os) with a Néel temperature T_N ～27.5 and 28.5 K, respectively. Their PCS conductance curves both exhibit a characteristic coherent double-peak-structure at temperatures below T_N, signaling an AFM gap around the Fermi surface. The temperature dependent AFM gap △₁ follows a Bardeen-Cooper-Schrieffer (BCS)-like mean-field behavior with a moderate gap anisotropy for PCS along different crystal axes. Another asymmetric gap-like feature is observed for both compounds at temperatures far below T_N, which is consistent with opening of a new hybridization gap △_h inside the long-range ordered AFM state. Our results suggest a common itinerant nature of the anomalous AFM ordering, constraining theoretical models to explain the AFM origin in CeRu₂Al₁₀ and CeOs₂Al₁₀.