This paper presents the results of specific-heat and magnetization
measurements, in particular their field-orientation dependence, on the first
discovered heavy-fermion superconductor CeCu2​Si2​ (Tc​∼0.6
K). We discuss the superconducting gap structure and the origin of the
anomalous pair-breaking phenomena, leading e.g., to the suppression of the
upper critical field Hc2​, found in the high-field region. The data
show that the anomalous pair breaking becomes prominent below about 0.15 K in
any field direction, but occurs closer to Hc2​ for H∥c. The
presence of this anomaly is confirmed by the fact that the specific-heat and
magnetization data satisfy standard thermodynamic relations. Concerning the gap
structure, field-angle dependences of the low-temperature specific heat within
the ab and ac planes do not show any evidence for gap nodes. From
microscopic calculations in the framework of a two-band full-gap model, the
power-law-like temperature dependences of C and 1/T1​, reminiscent of nodal
superconductivity, have been reproduced reasonably. These facts further support
multiband full-gap superconductivity in CeCu2​Si2​.Comment: 10 pages, 8 figures, published in Phys. Rev.