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Antiferromagnetic Néel temperatures (TN) are reported for magnetic rare earth cobalt compounds RCo4B4(R=Gd, Tb, Dy, Ho, Er, Tm) which crystallize with the primitive tetragonal CeCo4B4-type structure. The maximum TNof 3.68 K was observed in TbCo4B4, while TmCo4B4has the lowest ordering temperature of 0.17 K. No magnetic transition was observed for CeCo4B4and LuCo4B4down to 60 mK. The complex evolution from antiferromagnetic order in HoCo4B4(TN=1.91 K) to ferromagentic order in HoRh4B4(TC=6.56 K) of the pseudoternary system Ho(Rh1-xCox)4B4is briefly discussed.

Highly crystalline single phase "2122", Bi2CaSr2Cu2O8+?, sample with ?=0.25 has been prepared from citrate precursors with pyrolysis. Stable and bulk superconductivity with Tc(onset)=99 K and Tc(zero)=95 K was reproducibly detected by the magnetic susceptibility and electrical resistivity measurements, respectively.

Stable and reproducible superconductivity in the Tl(Ba2-xLax)CuO5-?(0.0?x?0.6) system with the tetragonal TlBa2CuO5-?-type (1021) structure was reported. A Prototype compound TlBa2CuO5-?had shown a metastable superconducting onset around 25 K, with zero resistivity at 10 K. With partial substitution of La for Ba ions, Tc(50% resistivity drop) increases to 45 K, Tc0(zero resistivity) to 42 K and onset around 50 K. A diamagnetic signal was observed with onset as high as 57 K. Tetragonal lattice parameters decrease with the increasing La concentration due to the partial replacement of larger Ba2+ions by smaller La3+ions. The Pairing field energy of 170 K and electron-elementary excitation coupling constant ? of 0.76 were derived from the BCS-like Tcformula through comparison with other single Tl-O layer systems TlCan-1Ba2CunO2n+3-?.