  We have synthesized polycrystalline and single crystal samples of PbCu3TeO7
and studied its properties via magnetic susceptibility chi(T) and heat-capacity
Cp(T) measurements and also electronic structure calculations. Whereas the
crystal structure is suggestive of the presence of a quasi-2D network of Cu2+
(S = 1/2) buckled staircase Kagome layers, the chi(T) data show magnetic
anisotropy and three magnetic anomalies at temperatures, TN1 ~ 36 K, TN2 ~ 25
K, TN3 ~ 17 K, respectively. The chi(T) data follow the Curie-Weiss law above
200 K and a Curie-Weiss temperature Theta_CW ~ -150 K is obtained. The data
deviate from the simple Curie-Weiss law below 200 K, which is well above TN1,
suggesting the presence of competing magnetic interactions. The magnetic
anomaly at TN3 appears to be of first-order from magnetization measurements,
although our heat-capacity Cp(T) results do not display any anomaly at TN3. The
hopping integrals obtained from our electronic structure calculations suggest
the presence of significant intra-Kagome (next-nearest neighbor and diagonal)
and inter-Kagome couplings. These couplings take the PbCu3TeO7 system away from
a disordered ground state and lead to long-range order, in contrast to what
might be expected for an ideal (isotropic) 2D Kagome system.
