The superconducting gap structure of PrOs₄ Sb₁₂ and CeRu₂ probed by C (H, φ{symbol})

We have performed measurements of the angle-resolved specific heat C (H, φ{symbol}) on PrOs₄ Sb₁₂ and the well-known s-wave superconductor CeRu₂ in order to gain information about their respective superconducting (SC) gap structure. PrOs₄ Sb₁₂ exhibits pronounced minima (maxima) in C (H, φ{symbol}) along the [1 0 0] ([1 1 1]) directions. CeRu₂ shows minima (maxima) along the [1 1 0] ([1 0 0]) directions. The field dependence of the oscillation amplitude of C (φ{symbol}), | A |, shows similar behavior for both suggesting finite minima in the SC gap, where C (φ{symbol}) is smallest. On the other hand, in comparison the temperature dependence of | A | shows aberrant behavior.