Field-orientation dependence of low-energy quasiparticle excitations in the heavy-electron superconductor UBe

Shimizu, Yusei*; Kittaka, Shunichiro*; Sakakibara, Toshiro*; Haga, Yoshinori   ; Yamamoto, Etsuji  ; Amitsuka, Hiroshi*; Tsutsumi, Yasumasa*; Machida, Kazushige*

Low-energy excitation in the superconducting state of UBe were studied by means of specific-heat measurements in a rotating field. Quite unexpectedly, the magnetic-field dependence of specific heat is linear in field at low fields with an isotropic field-angle dependence. The observation implies that the gap is fully open over the Fermi surfaces, in contrast to the previous expectation.