Distinct Kondo Screening Behaviors in Heavy Fermion Filled Skutterudites with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mn>4</mml:mn><mml:msup><mml:mi>f</mml:mi><mml:mn>1</mml:mn></mml:msup></mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mn>4</mml:mn><mml:msup><mml:mi>f</mml:mi><mml:mn>2</mml:mn></mml:msup></mml:math> Configurations

Filled-skutterudite heavy fermion (HF) compounds host rich ground states depending on the f electron configurations. CeOs4Sb12 (COS) with Ce 4f1, and PrOs4Sb12 (POS) Pr 4f2 configurations show distinct properties of Kondo insulating HF superconductivity, respectivity. We unveiled underlying microscopic origin by angle-resolved photoemission spectroscopy studies. Their eV-scale band structure matches well, representing common characters conduction electrons in ROs4Sb12 systems (R = rare earth). However, interact differently them. Strong hybridization between is observed COS dependent gaps, development state directly revealed. Although POS a singlet, finite but incoherent exists due to scattering thermally excited triplet crystalline electric field (CEF) state. Our results help understand intriguing POS, provide clean demonstration differences 4f1