The benchmark, agreed earlier in the week between one the world’s biggest zinc producers and the South Korean processor, included a reduction in the amount that smelters pay for silver, a byproduct in zinc concentrates, the sources said. A payable for germanium will now apply in the benchmark for this year, unlike in the past, when it was not part of the byproduct payables, two sources said. Fastmarkets has, however, heard conflicting accounts about the byproduct payables since March 6.