After much research I have dared the experiment and brought me the Lenovo adapter. Without driver works well this not Win 8. For the Yoga 13, there is no explicit driver, so I installed the driver for the ThinkPad X1 Carbon and downloaded me: it works !! :-) Can now also operate via Ethernet the Yoga13.
The download link:
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Btw .: The processing of the plug is far better and more solid than that of BobGear.