Phenomenological trends for heavy Fermi liquids and narrow-band metals

A phenomenological correlation is presented for the magnetic susceptibility * and the electronic heat-capacity coefficient * of a large number of narrow-band and heavy-fermion metals. A novel method of plotting */* vs * reveals quantitative boundaries for distinct regions of superconducting, magnetically ordered, and paramagnetic ground states. It is suggested that magnetic interactions are a primary limitation for the Tc of conventional superconductors, whereas a more delicate interplay exists between magnetic order, paramagnetism, and superconductivity above a threshold value of * which defines the onset of magnetic order.