Breakup of Heavy Fermions on the Brink of "Phase A" in CeCu2Si2

We report resistivity, $\ensuremath{\rho}(T)$, and specific-heat, $C(T)$, results on near stoichiometric $\mathrm{CeCu}{}_{2}{\mathrm{Si}}_{2}$ samples, in the vicinity of a quantum critical point (QCP). The latter is defined by ${T}_{A}\ensuremath{\rightarrow}0$, where ${T}_{A}\ensuremath{\lesssim}0.8\mathrm{K}$ marks the transition into a spin-density--wave-type ``phase $A$'' which competes with heavy-fermion superconductivity below ${T}_{c}\ensuremath{\approx}0.65\mathrm{K}$. Upon approaching the QCP, $\ensuremath{\rho}(T)$ and $C(T)$ behave very disparately, suggesting a breakup of the heavy quasiparticles. Very surprising observations are being made for samples with ${T}_{A}g0$ also.