I've found a chapter about etherchannel in IOS XE switching config guide
one specific feature of ASR is the per vlan load sharing.
the interface configuration guide for IOS XE actually sends to a generic IOS page
Hope to help
I had an issue where traffic would not traverse the etherchannel from an ASR1k to a 4900M catalyst. The issue was ultimately the missing command that is mandatory it seems in etherchannel for ASR.
port-channel load balencing vlan-manual I believe it was. Once i popped that in there on default the link came up and protocol established across the PO.
Mine was a l3 so I had to throw a tagged sub interface on the PO1 and tag it on the 4900 side also.